1. NACE Standard_TM0212-2012 Detection Testing

NACE Standard TM0212-2012 Item No. 21260

Standard Test Method Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by letters patent, or as indemnifying or protecting anyone against liability for infringement of letters patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE interpretations issued by NACE in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE standards are subject to periodic review, and may be revised or withdrawn at any time in accordance with NACE technical committee procedures. NACE requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication and subsequently from the date of each reaffirmation or revision. The user is cautioned to obtain the latest edition. Purchasers of NACE standards may receive current information on all standards and other NACE publications by contacting the NACE FirstService Department, 1440 South Creek Dr., Houston, TX 77084-4906 (telephone +1 281-228-6200). Approved 2012-06-23 NACE International 1440 South Creek Drive Houston, TX 77084-4906 +1 281-228-6200 ISBN 1-57590-255-9 ©2012, NACE International

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TM0212-2012

_________________________________________________________________________ Foreword Microbiologically influenced corrosion (MIC) is corrosion affected by the presence or activity (or both) of microorganisms in biofilms on the surface of the corroding material. Many materials, including most metals and some nonmetals, can be degraded in this manner. Microbiologically mediated reactions can alter both rates and types of electrochemical reactions in a corrosion cell. These reactions influence pitting, crevice corrosion, differential aeration cells, concentration cells, dealloying, and galvanic corrosion. Therefore, MIC investigations require microbiological, chemical, and metallurgical testing for proper diagnosis. The conclusion that MIC has taken place should be based on the preponderance of circumstantial evidence. Microorganisms are often resistant to many control methods and can pose a serious internal corrosion threat for pipelines. This NACE standard test method applies to the internal surfaces of pipelines, and describes types of microorganisms, mechanisms by which MIC occurs, methods for sampling and testing for the presence of microorganisms, research results, and interpretation of test results. Sections 1 through 4 of this standard discuss the technical aspects of MIC. Sections 5 through 7 discuss field equipment and testing procedures. This standard is intended for use by pipeline operators, pipeline service providers, government agencies, and any other persons or companies involved in planning or managing pipeline integrity. Portions of Section 3 and Section 4 of this standard are excerpted from Peabody’s Control of 1 Pipeline Corrosion, Chapter 14, “Microbiologically Influenced Corrosion.” This standard test method was prepared by Task Group (TG) 254, “Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines: Detection, Testing, and Evaluation—Standard Test Method.” TG 254 is administered by Specific Technology Group (STG) 35, “Pipelines, Tanks, and Well Casings.” This standard is issued by NACE under the auspices of STG 35.

In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual. The terms shall and must are used to state a requirement, and are considered mandatory. The term should is used to state something good and is recommended, but is not considered mandatory. The term may is used to state something considered optional.

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TM0212-2012

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NACE International Standard Test Method Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines Contents 1. General ........................................................................................................................... 1 2. Definitions ....................................................................................................................... 1 3. Introduction ..................................................................................................................... 4 4. Internal Microbiologically Influenced Corrosion of Pipelines........................................... 7 5. Sampling Equipment ....................................................................................................... 7 6. Sampling Programs and Procedures .............................................................................. 8 7. Testing Guidelines ........................................................................................................ 14 8. Corrosion Monitoring ..................................................................................................... 20 9. Application of Test Methods to Pipelines and Interpretation of Data ............................ 23 References ........................................................................................................................ 25 FIGURES: 17 Figure 1: Examples of various pit morphologies as viewed in cross section. ............... 11 Figure 2: An illustration of the portions of the different pools of microorganisms (live, inactive, and dead) typically present in samples from the oil industry that are enumerated using various MMMs compared to the MPN (culturing) method. Each of 29 the methods indicated is discussed further in the text. ............................................ 18 Figure 3: Appendix A: Site Inspection and Testing Checklist (Nonmandatory) ............................... 29 Appendix B: Example of Pipeline System Assay Data (Nonmandatory) .......................... 32 TABLE 1 ............................................................................................................................ 17 Table A1: Site Inspection and Testing Checklist .............................................................. 29 Table B1: Example of Pipeline System Assay Data ......................................................... 32 _________________________________________________________________________

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TM0212-2012 _________________________________________________________________________ Section 1: General 1.1 While the evaluation, monitoring, and mitigation of MIC cannot be prescribed in one particular manner for any given pipeline, this standard describes methodologies by which the appropriate tools and techniques may be selected and practically applied. The methods presented in this standard represent the general consensus of industry experts in pipeline corrosion and microbiology at the time this standard was published. 1.2 Appendix A (Nonmandatory) provides a site inspection and testing checklist and Appendix B (Nonmandatory) provides an example of pipeline system assay data. 1.3 All applicable safety and environmental codes, rules, and regulations must be followed when using this standard. 1.4 The term “pipeline” as used in this standard generally refers to any pipe, tank, vessel, or component of a pipeline system for which the mechanism of internal MIC is of interest to the user of this standard.

_________________________________________________________________________ Section 2: Definitions (1)

The definitions of many of the corrosion-related terms used in this test method can be found in NACE/ASTM terms not included therein that have been used in this test method are defined as follows:

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G193.

Other

Abiotic: The absence of living organisms, their biological components, or the metabolic activities of living organisms. Acid-producing bacteria (APB): Aerobic or anaerobic bacteria that produce organic acids as an end product of their metabolism. A few organisms (e.g., Thiobacillus), also are capable of producing mineral acids (typically under aerobic conditions). Aeration: (1) Exposing to the action of air. (2) Causing air to bubble through. (3) Introducing air into a solution by spraying, stirring, or similar method. (4) Supplying or infusing with air, as in sand or soil. (5) The introduction of air into the pulp in a flotation cell to form air bubbles. Aerobic: Containing air or free molecular oxygen. Aerobic microorganism (aerobe): A microorganism that uses oxygen as the final electron acceptor in metabolism. Anaerobic microorganism (anaerobe): A microorganism that does not require oxygen for metabolism. Archaea: Unicellular microorganisms that are genetically distinct from bacteria and eukaryotes, which often inhabit extreme environmental conditions. Archaea include halophiles (microorganisms that may inhabit extremely salty environments), methanogens (microorganisms that produce methane), and thermophiles (microorganisms that can thrive in extremely hot environments). Archaeoglobus is a common Archaea. Archaeoglobus: Microorganisms that grow at high temperatures between 60 and 95 °C, with optimal growth at 83 °C (ssp. A. 3 fulgidus VC-16). They are sulfate-reducing Archaea, coupling the reduction of sulfate to sulfide with the oxidation of many different organic carbon sources, including complex polymers. Archaeoglobus species have been isolated from oil reservoirs and production systems; however, this group of microorganisms is normally not measured with current culturing techniques. Autoclave: A pressurized, steam-heated vessel used for sterilization. Biofilm: Microbial growth at an interface in which individual cells are bound within a matrix of extracellular polymeric materials. Biotic: Involving the presence or metabolic activities of living organisms.

(1)

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TM0212-2012 Carbohydrate: Any of the group of organic compounds composed of carbon, hydrogen, and oxygen, including sugars, starches, and celluloses. Culture medium: A sterile solution or other substrate formulated to promote the growth of a particular type or group of microorganisms. (Also called growth medium.) 4-,6-diamidino-2-phenylindole (DAPI): A stain for optical microscopy that targets the Deoxyribonucleic acid (DNA) in all (i.e., living and inactive) microbial cells. Denaturing gradient gel electrophoresis (DGGE): A molecular microbiological method used to profile the most abundant microbial groups in a sample. Dissimilatory: Metabolic reactions in which a reductant is used as an electron acceptor and material is not incorporated into the cell (e.g., dissimilatory sulfate or nitrate reduction); metabolic changes that convert complex molecules into simple ones. Eukaryotes: Cells having a true nucleus, bound by a double membrane. Prokaryotic cells have no nucleus. Facultative: Capable of growing either with or without the presence of a specific environmental factor, e.g., oxygen. Fluorescence in situ hybridization (FISH): A molecular microbiological method used for enumeration of microorganisms. The method is based on gene probes targeting ribosomal Ribonucleic acid (RNA) (16S or 23S rRNA) in microbial cells. Only living and active cells contain sufficient ribosomes that can be detected by FISH. Gene probes consist of two parts: (1) an artificial DNA strand complementary to the ribosomal RNA in the target cell; and (2) a fluorescing molecule covalently attached to the probe that enables observation of the target microorganism in the microscope. Fungi: Nucleated, usually filamentous, spore-bearing parasitic microorganisms devoid of chlorophyll, which include molds, mildews, smuts, mushrooms, yeasts, and others. Fungi are often found to degrade fuel (e.g., fuel spoilage). Growth: An increase in the quantity of metabolically active protoplasm, accompanied by an increase in cell numbers, cell size, or both. Growth medium: See culture medium. Inoculum: A small quantity of microorganisms used to start a new culture. Inorganic acid: A compound composed of hydrogen and a nonmetal element or radical; examples are hydrochloric acid (HCl) and sulfuric acid (H2SO4). A substance that yields hydrogen ions when dissolved in water and that can act as a proton donor. Isotonic: A solution that has uniform tension; having the same osmotic pressure as the fluid phase of a cell or tissue. +3)

+4

Metal-reducing bacteria (MRB): Bacteria that in direct contact with solid iron (Fe and manganese (Mn ) oxides produce +2 +2 1 soluble ions (Fe and Mn ) resulting in dissolution of surface oxides and localized corrosion. Methanogens: Microorganisms that produce methane as a metabolic by-product in anoxic (i.e., oxygen-free) conditions. They are classified as Archaea, a group quite distinct from bacteria. Some are extremophiles and found in environments such as oilfield systems, hot springs, and submarine hydrothermal vents, as well as in the “solid” rock of the Earth's crust, kilometers below the surface. Methanogens are common Archaea in oil production systems; however, they are normally not measured with current culturing techniques. Methanogens are involved in MIC by consuming hydrogen at the metal surface and thereby creating a depolarization. Microaerophilic: Pertains to those microorganisms that require free oxygen but in very low concentrations for optimum growth. Microbe: See microorganism. Microbiologically influenced corrosion (MIC): Corrosion affected by the presence or activity, or both, of microorganisms. (The microorganisms that are responsible for MIC are typically found in biofilms on the surface of the corroding material. Many materials, including most metals and some nonmetals, can be degraded in this manner.)

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TM0212-2012 Microorganism: An organism of microscopic or ultramicroscopic size. Bacteria, Archaea, and fungi are microorganisms. Bacteria and Archaea are combined and called prokaryotes. Fungi belong to eukaryotes (Eukarya). Monosaccharide: A carbohydrate that cannot be hydrolyzed to a simpler carbohydrate. Morphology: A branch of biology that deals with the structure and form of an organism at any stage of its life history. Most probable number (MPN) method: A technique that does not rely on quantitative assessment of individual cells; instead, it relies on specific qualitative attributes of the microorganism being counted. The important aspect of MPN methodology is the ability to estimate a microbial population size based on a process-related attribute. The MPN technique estimates microbial population sizes in a liquid substrate. The methodology for the MPN technique is dilution and incubation of replicated cultures across several serial dilution steps. Motile: Exhibiting or capable of movement. Organic acid: Weak acid that contains carbon (correctly classified as a carboxylic acid because it contains –COOH, a carboxyl group). Organic acids (e.g., formic, acetic, lactic) are the end product of metabolism by a variety of microorganisms. (Also called short-chain fatty acids.) Organism: A complex structure of interdependent and subordinate elements whose relations and properties are largely determined by their function as a whole. (Also see microorganism.) Phosphate buffer: A solution made of dibasic potassium phosphate (K2HPO4) and sodium phosphate (Na2HPO4). Polymerase chain reaction (PCR): A molecular technique that allows the production of large quantities of a specific DNA from a DNA template using a simple enzymatic reaction without a living organism. A quantitative version of PCR is called Quantitative polymerase chain reaction (qPCR). Polysaccharide: A carbohydrate composed of many monosaccharides. Prokaryotes: The prokaryotes are divided into two domains: the bacteria and the Archaea. Archaea were originally thought to live only in inhospitable conditions such as extremes of temperature, pH, and radiation, but have been found in all types of habitats. Sulfate-reducing prokaryotes (SRP) consist of both sulfate-reducing bacteria and sulfate-reducing Archaea. Quantitative polymerase chain reaction (qPCR): A molecular microbiological method used to quantify the total number of microorganisms or a specific genus/species of microorganisms in nearly any type of sample. qPCR can be used for both fluid and solid samples, as well as microorganisms collected via membrane filtration. This method does not underestimate microorganisms that do not grow in culture. This method uses synthetic DNA (called primers) tagged with a fluorescent molecule or synthetic DNA mixed with a DNA intercalating agent (dye) to quantify microorganisms using a modified version of polymerase chain reaction (PCR). Ringer’s solution: An aqueous solution of chlorides that is isotonic to animal tissues. Robbins Device: A tool to provide samples of biofilms growing on submerged surfaces, typically consisting of a long chamber through which the test fluid flows, exposing a number of removable plugs or coupons to the test conditions. Sampling Thief: Also called a sampling bomb, a device used to collect samples from the bottom or at different depths in large tanks. Sterile: (1) Free of any living microorganisms. (2) Not introducing microorganisms that are foreign to the host body or subject under study. Substratum: A solid surface; often refers to a surface colonized by microorganisms. Sulfate-reducing Archaea (SRA): A group of anaerobic Archaea that perform dissimilatory reduction of sulfate, resulting in sulfide formation. They are most likely to grow at reservoir conditions (60 to 95 °C). Sulfate-reducing bacteria (SRB): A group of anaerobic bacteria that perform dissimilatory reduction of sulfate, resulting in sulfide formation. They grow at a broad range of temperatures.

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TM0212-2012 Sulfate-reducing prokaryotes (SRP): A group of microorganisms that consists of both sulfate-reducing bacteria (SRB) and sulfate-reducing Archaea (SRA).

_________________________________________________________________________ Section 3: Introduction 3.1 MIC is corrosion affected by the presence or activity (or both) of microorganisms in biofilms on the surface of the corroding material. Many materials, including most metals and some nonmetals, can be degraded in this manner. MIC can result from the 1 activities of microorganisms, including bacteria, Archaea, and fungi in biofilms or in the local environment directly in contact with 4 the corroding material. This standard is primarily focused on the effects of bacteria and Archaea in oilfield systems. The following general statements are common facts regarding microorganisms. 3.1.1 Individual microorganisms are usually small in size—they are typically 0.2 to 10 µm (8 to 400 µin) in length by up to 2 or 3 µm (80 or 120 µin) in width. This quality allows them to penetrate crevices and other areas. Colonies of microorganisms 1 can grow to macroscopic proportions. 3.1.2 Microorganisms may be motile, capable of migrating to more favorable conditions or away from less favorable conditions (e.g., toward energy sources or away from toxic materials). 3.1.3 Microorganisms have specific receptors for certain chemicals. This allows them to seek higher concentrations of substances that may represent food sources. Nutrients, especially organic nutrients, are generally in short supply in most aquatic environments, but are concentrated on surfaces, including metals. Organisms able to find and establish themselves 1 on surfaces have a distinct advantage in nutrient-deficient environments. 3.1.4 Certain microorganisms can withstand a wide range of temperatures (at least –10 to 99 °C [14 to 210 °F]), pH levels, 1 and oxygen concentrations. 3.1.5 Microorganisms grow in colonies and form biofilms, making survival more likely under adverse conditions. 3.1.6 Under favorable conditions, microorganisms can reproduce very quickly (generation times of 18 minutes have been 1 reported). 3.1.7 Individual microbial cells can be widely and quickly dispersed by water and other modes, thus the potential for some cells in the population to reach more favorable environments is good. 3.1.8 Many microorganisms can quickly adapt to use a wide variety of nutrient sources. For example, Pseudomonas fluorescens can use more than 100 different compounds as sole sources of carbon and energy, including sugars, lipids, 1 alcohols, phenols, and organic acids. 3.1.9 Many microorganisms form extracellular polysaccharide materials (capsules or slime layers). The resulting slimes are sticky and trap organisms and debris (food), resist penetration of toxicants (e.g., biocides or corrosion inhibitors), and hold 1 the cells between the source of the nutrients (the bulk fluid) and the surface. 3.1.10 Many bacteria and fungi produce spores that are resistant to temperature, acids, alcohols, disinfectants, drying, freezing, and other adverse conditions. Spores may remain viable for hundreds of years and germinate on finding favorable conditions. In the natural environment, there is a difference between survival and growth. Microorganisms can withstand long periods of starvation and desiccation. If exposed to alternating wet and dry conditions, microbes may survive dry periods and grow only during the wet periods. 3.1.11 Microorganisms may be resistant to many chemicals (antibiotics, disinfectants, and others) by virtue of their ability to degrade these chemicals or by being impenetrable (because of slime, cell wall, or cell membrane characteristics). Resistance may be easily acquired by mutation or acquisition of a plasmid (essentially by a naturally occurring genetic exchange between cells—i.e., genetic engineering in the wild). 3.2 Mechanisms for MIC MIC typically takes place in the presence of microbial consortia that are comprised of more than one physiological type of microorganism. Depending on the environment, these microbes may include metal-oxidizing bacteria, sulfate-reducing

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TM0212-2012 prokaryotes (SRP), acid-producing bacteria (APB), metal-reducing bacteria (MRB), and methanogens that interact in complex 5,6 ways within the structure of biofilms. Based on visual examination, MIC does not produce a unique form or morphology of corrosion. Instead, MIC can result in pitting, crevice corrosion, underdeposit corrosion, and dealloying, in addition to galvanic corrosion. Simply by their presence on a metal surface, microorganisms may establish the proper conditions for pitting or crevice corrosion. Once localized corrosion has been initiated, microbial reactions can maintain suitable conditions (e.g., low oxygen concentration) for continued pit/crevice growth. Under anaerobic reducing conditions, MIC may be observed when there is some mechanism for the removal or transformation of corrosion products (e.g., a transition from stagnation to flow) or the introduction of oxygen to a previously anaerobic environment. 3.2.1 Sulfate Reduction Sulfate-reducing bacteria (SRB) are a diverse group of anaerobic microorganisms that can be isolated from a variety of subsurface environments. If the aerobic respiration rate within a biofilm is greater than the oxygen diffusion rate during biofilm formation, the metal/biofilm interface can become anaerobic and provide a niche for sulfide production by SRB. The critical thickness of the biofilm required to produce anaerobic conditions depends on the availability of oxygen and the rate of respiration. SRB concentrations may be proportional to sulfate concentrations. The distribution of favorable pH ranges from 6 to 12, although SRB can adapt to other less optimum conditions. SRB grow in fresh water or salt water under anaerobic conditions. Many species of SRB, differing in morphology and in the organic substances they can metabolize, have been identified. They have in common the ability to oxidize certain organic substances to organic acids or carbon dioxide by reduction of inorganic sulfate to sulfide. In the absence of oxygen, the metabolic activity of SRB causes accumulation of hydrogen sulfide near metal surfaces. This is particularly evident when metal surfaces are covered with biofilms. The concentration of sulfide is highest near the metal surface. Iron sulfide forms quickly on carbon steels and covers the surface if both ferrous and sulfide ions are available. Formation of iron sulfide minerals stimulates the cathodic reaction. Once electrical contact is established, a galvanic couple develops with the mild steel surface as an anode, and electron transfer occurs through the iron sulfide. Under conditions such as low ferrous ion concentrations, adherent and temporarily protective films of iron sulfides are formed on the steel surface, with a 7,8 consequent reduction in corrosion rate. Although SRB are anaerobic in their metabolism, studies by Hardy and Brown demonstrated that the availability of oxygen 9 can increase corrosion in the presence of SRB. They found that the corrosion rates of carbon steel in anaerobic cultures of SRB were low (7.0 μm/y [0.3 mpy]) while subsequent exposure to air caused higher corrosion rates (610 μm/y [24 mpy]). 10

The most prevalent mechanism for the observed corrosion in a study reported by Jack, et al. was the formation of a galvanic couple between steel and microbiologically produced iron sulfides. The couple is normally short-lived because the iron sulfide matrix becomes saturated with electrons derived from the corrosion process. In the presence of SRB, however, the corrosion process is perpetuated because SRB removes electrons (in the corrosion process) from the iron sulfide surface. This process may involve the formation of cathodic hydrogen on the iron sulfide or the direct transfer of electrons from the iron sulfide matrix to redox proteins in the bacterial cell wall. Corrosion rates associated with this mechanism were proportional to the amount of iron sulfide in the corrosion cell. Sulfate-reducing Archaea (SRA) are like SRB, obtaining their energy by oxidizing organic compounds or molecular hydrogen 11 (H2) while reducing sulfates to sulfides, especially to hydrogen sulfide. SRA consist of the genera Archaeoglobus. Archaeoglobus grow at temperatures in the range of 60 to 95 °C (140 to 203 °F), with optimal growth at 83 °C (181 °F) (ssp. 3 A. fulgidus VC-16). Previously, Archaeoglobus species have been isolated from oil reservoirs and oil production systems; however, this group of microorganisms is normally not measured with current culturing techniques. SRA are known to cause the corrosion of iron and steel in oil and gas processing systems by producing iron sulfide. The formation of H2S by SRA activity can have profound effects in terms of reservoir souring, health/safety/environmental threats, and materials degradation. 3.2.2 Acid Production Organic acids are produced by both bacteria and fungi. This process is anaerobic for some microorganisms, and aerobic for other microorganisms and fungi. Most final products of APB are short-chain fatty acids (e.g., acetic, formic, and lactic acids). 12 The role of APB in MIC is controversial. Pope, et al. proposed that APB produce biogenic organic acids that are directly

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TM0212-2012 13

responsible for corrosion in the absence of SRB. Jack, et al. reported that the main role of APB is to provide the environment and nutrients for SRB growth. Other bacterial species can produce aggressive inorganic acids, such as sulfuric acid (H2SO4), in aerobic environments. Microorganisms can generate locally high concentrations of carbon dioxide. The carbon dioxide dissolves in the water, producing carbonic acid. Carbonic acid solution is corrosive to pipeline steels and can 1 lead to general corrosion, pitting, and stress corrosion cracking. 3.2.3 Metal Deposition 3.2.3.1 Microorganisms can also affect corrosion by creating differential aeration cells on the surface of the metal and fixing the location of anodic sites beneath colonies of microorganisms. The organisms most often cited as causing differential aeration cells are those organisms capable of depositing iron and manganese oxides. 3.2.3.2 Iron-oxidizing bacteria produce orange-red tubercles of iron oxides and hydroxides by oxidizing ferrous ions from the bulk medium or the substratum. Iron-depositing bacteria are microaerophilic and may require synergistic associations with other bacteria to maintain low oxygen conditions in their immediate environment. Deposits of cells and metal ions create oxygen concentration cells that effectively exclude oxygen from the area immediately under the deposit and initiate a series of events that individually or collectively are very corrosive. In an oxygenated environment, the area immediately under individual deposits becomes deprived of oxygen. That area becomes a relatively small anode compared to the large surrounding oxygenated cathode. Cathodic reduction of oxygen can result in an increase in pH of the solution in the vicinity of the metal. The metal forms metal cations at anodic sites. If the metal hydroxide is the thermodynamically stable phase in the solution, the metal ions are hydrolyzed + by water, forming hydrogen (H ) ions. If cathodic and anodic sites are separated from one another, the pH at the anode decreases and that at the cathode increases. The pH at the anode depends on specific hydrolysis reactions. In addition, chloride (Cl–) ions from the electrolyte migrate to the anode to neutralize any buildup of charge, forming heavy metal chlorides that are extremely corrosive. Under these circumstances, pitting involves the conventional features of differential aeration, a large cathode-to-anode surface area, and the development of acidity and metallic chlorides. Pit initiation depends on mineral deposition by microorganisms. 3.2.3.3 Manganese oxidation and deposition is coupled to cell growth and metabolism of organic carbon. The reduced +2 form of manganese (Mn ) is soluble and the oxidized forms (Mn2O3, MnOOH, Mn3O4, and MnO2) are insoluble. As a result of microbial action, manganese oxide deposits are formed on buried or submerged materials including metal, stone, glass, and plastic, and can occur in natural waters that have manganese concentrations as low as 10 to 20 ppb. For mild steel corrosion under anodic control, manganese oxides can elevate corrosion current. The current can be significant for biomineralized oxides that provide large mineral surface areas. Given sufficient conductivity, manganese oxide can sometimes serve as a cathode to support corrosion at an oxygen-depleted anode within the deposit. 3.2.4 Metal Reduction Dissimilatory iron and/or manganese reduction occurs in several microorganisms, including anaerobic and facultative aerobic +3 +4 bacteria. Inhibitor and competition experiments suggest that iron (Fe ) and manganese (Mn ) are efficient electron acceptors that are similar to nitrate in redox ability and are capable of out-competing electron acceptors of lower potential, 9 +3 +4 +2 such as sulfate or carbon dioxide. MRB in direct contact with solid Fe and Mn oxides produce soluble ions (Fe and +2 1 Mn ).” The result is dissolution of surface oxides and localized corrosion. 3.2.5 Methanogens Methanogens produce methane as a metabolic by-product in anoxic conditions. They are classified as Archaea, a group quite distinct from bacteria. 2

Methanogens typically thrive in environments in which all electron acceptors other than CO (such as oxygen, nitrate, sulfate, and trivalent iron) have been depleted. They are common in wetlands, where they are responsible for marsh gas, and in the guts of animals such as ruminants and humans. Others are extremophiles, found in environments such as oilfield systems, hot springs, and submarine hydrothermal vents, as well as in the “solid” rock kilometers below the surface of the Earth's crust. Methanogens are common Archaea in oil production systems; however, they are normally not measured with current 4,14 culturing techniques.

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TM0212-2012 Methanogens are known to promote MIC in steel and other metal structures by consuming hydrogen formed at the corrosion 15 cathode.

_________________________________________________________________________ Section 4: Internal Microbiologically Influenced Corrosion of Pipelines 4.1 Internal Environment 4.1.1 For pipelines transporting natural gas, petroleum products, crude oil, or other organic liquids, internal corrosion, including MIC, may occur at locations where water is frequently present. Water may be present as a liquid component of the pipeline contents; may result from condensation of water vapor in a gas phase; or may be absorbed in or adsorbed on solids. 4.1.2 Pipelines transporting water or aqueous fluids such as brine, waste water, or produced water may experience MIC and/or other types of internal corrosion at locations throughout the pipeline system that are difficult to predict. 4.1.3 Pipeline system components such as tanks, vessels, slug catchers, drip legs, and pig traps may provide locations where water can accumulate and result in conditions suitable for MIC or other internal corrosion mechanisms. 4.1.4 Microorganisms can exist in extremely small volumes of water; thus even in pipelines that are considered to be normally “dry” or for which the contents contain essentially no water during normal operations, isolated internal MIC can occur where thin films of water become trapped beneath deposits or organic matter. 4.1.5 Pipeline design features may create locations for water accumulation, such as topographical low points, drips, crossings, or dead legs, and should be considered potential locations for MIC or other internal corrosion mechanisms. 4.2 Operating Conditions 4.2.1 System upsets that introduce water, or contribute new energy sources for microorganisms established in the pipeline, can affect MIC of pipelines. 4.2.2 Fluid velocity can affect the establishment of biofilms. Stagnant or quiescent conditions may favor the establishment of biofilms as opposed to locations in the pipeline with higher superficial velocity. 4.2.3 Locations where mitigation actions such as inhibitor injection, maintenance pigging, and biocide application are performed may affect biofilms and the location of biotic and/or abiotic localized corrosion mechanisms. 4.2.4 Points of entry or exit of process fluids may affect the occurrence or severity of internal corrosion mechanisms, such as MIC. 16

4.2.5 Pipelines also can be affected by external MIC. Testing for external MIC is covered in NACE Standard TM0106.

_________________________________________________________________________ Section 5: Sampling Equipment 5.1 Various procedures may be used to collect samples for microbiological testing. Typical equipment and supplies should include some or all of the following: (a) Sterile plastic or glass collection containers (10 to 125 mL); (b) Sterile plastic sample collection bags; (c) Sterile metal scalpels; (d) Sterile cotton or polyester-fiberfill swabs; (e) Sterile wooden spatulas (tongue depressors); (f)

Sterile 1 to 5 mL syringes;

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TM0212-2012 (g) Sterile disposable plastic pipettes; (h) Sterile latex gloves; (i)

Ice chest with refrigerant;

(j)

Digital or film camera;

(k) Magnifying lens (5X to 60X) or macro function; (l)

Marking pens (for wet surfaces);

(m) Nylon bristle brushes; (n) Mechanical pit depth gauge; (o) Labels; (p) pH paper or meter; (q) Culture media; (r)

Ultrasonic testing (UT) meter to measure metal thickness;

(s) Sterile vials of phosphate-buffer solution; and (t)

Formaldehyde (36.5%) for fixation on site (for use with DAPI method) or 2% Glutaraldehyde as a general fixative.

5.2 Sterile sample collection containers must not contain any chemical that inhibits microbial survival. Collection containers may contain sterile phosphate buffer, Ringer’s solution, or other holding medium for suspension of solid samples. If samples are to be analyzed for chemical composition, they must be maintained separately from samples transferred to a holding medium. Most sample collection containers are glass or plastic. 5.2.1 Glass sample collection containers should have screw caps and must have been sterilized using a combination of pressure and temperature over time (e.g., autoclaved at a gauge pressure of 100 kPa [14.5 psig], steam-heated at approximately 121 °C [250 °F] for a minimum of 20 min). Glass sample collection containers may be reused many times after cleaning and sterilization. 5.2.2 Plastic sample collection containers are usually disposable; however, some may be cleaned and autoclaved. In most cases, plastic sample collection containers have rigid walls, but polyethylene flexible-walled containers with closure ties may be used. 5.2.3 Sterile plastic bags provide a lightweight sample collection container. Plastic bags designed for domestic use are not sterile and must not be used for sample collection. 5.2.4 Sterile, individually wrapped supplies may be purchased from most pharmacies and all scientific supply stores. Sterile plastic bags are usually ordered in bulk, and the interiors remain sterile until opened.

_________________________________________________________________________ Section 6: Sampling Programs and Procedures 6.1 Purpose of Sampling Samples may be collected for the purposes of assessing or monitoring conditions in a pipeline, in support of mitigation activities, or for other purposes. When personnel are working with potentially hazardous materials, all applicable health, environmental, and safety regulations must be followed. 6.2 Sampling Programs

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TM0212-2012 6.2.1 Because of normal statistical variations associated with sample collection and microbiological testing, more reliable data typically result from performing tests on samples collected over a period of time, rather than from any single sample. 6.2.2 In general, sampling and testing programs should be designed to collect information about operating conditions, corrosion rates, and microbiological conditions over a period of time to look for trends in the findings. 6.2.3 To determine the existence or significance of an internal MIC threat to a pipeline, microbiological test results should be integrated with other data relevant to conditions associated with internal corrosion. Examples of data that should be collected at the time of sample collection and between times of sample collection for integration with microbiological test results include: 6.2.3.1 Operating conditions such as pressure, temperature, flow rate, treatment chemical injection rates, and pigging frequency; 6.2.3.2 Chemical composition data from the gas, liquids, and solids transported; and 6.2.3.3 Data from corrosion coupons, probes, or routine inspections that describe the corrosion rate, pitting rate, or rate of metal loss measured on the pipeline. 6.2.4 Sampling data collection and analysis should be directed toward distinguishing the contributing effects of both biotic and abiotic factors on the likelihood, severity, location, and cause of internal corrosion. 6.2.5 In the investigation of internal corrosion on a pipe section or component removed from service, samples for microbiological testing may have been altered or contaminated during the process of removal. Whenever possible, samples for microbiological testing also should be collected from unaltered equipment in the same service as that of the removed pipe section or component for comparison. 6.3 Sources and Types of Samples 6.3.1 Samples collected for the purposes of characterizing the physical, chemical, and microbiological conditions present in a pipeline should be obtained from locations suitable for providing accurate, meaningful data. Sample locations identified as part of a program for assessing or monitoring internal MIC should take into account any local factors affecting the chemical composition and microbiological environment. Sample locations in stagnant piping (e.g., dead legs) may have significant differences in chemical and microbiological conditions compared to sample locations in flowing pipelines. Changes in internal pressure at different sample locations can result in variations in the concentration of gases in the solution. 6.3.2 Sample locations should be selected based on knowledge of the current and historical operating conditions of the pipeline. Conditions that should be considered include: 6.3.2.1 The physical nature of the available samples: gas, liquid, solid, temperature, pressure, flow rate; 6.3.2.2 The availability of internal corrosion monitoring data or inspection data for the pipe section or component associated with the sample location; 6.3.2.3 The potential for collecting bulk fluid and surface-related samples from the same location; 6.3.2.4 A history of operating problems or leaks for the pipe section or component associated with the sample location; 6.3.2.5 A sample location relative to mitigation activities such as maintenance pigging, chemical treatment with biocide or corrosion inhibitors, methanol injection, emulsion breaker, or scale inhibitor; 6.3.2.6 The accessibility for repeat sample collection; 6.3.2.7 The ability to safely and reliably collect a sample; and 6.3.2.8 Limiting impact on normal operation of the pipeline. 6.3.3 Samples also may be collected during occasional or routine pipeline maintenance activities, such as the retrieval of cleaning pigs, blowing or draining of vessels, removal of corrosion coupons, or the collection of fluid samples for environmental or contractual testing.

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TM0212-2012 6.3.4 In general, liquid samples should be collected when personnel are attempting to characterize conditions in liquid pipelines or in gas pipelines where liquids may exist. Liquid samples should be evaluated with particular emphasis on any water phase present, because water is crucial to both the chemical and microbial influences on corrosion. Liquid also may be sampled concurrently with solids or sludge, and distinction between the liquid and solid phases should be made during subsequent testing and analysis. The use of water-finding test paper may be beneficial in establishing whether an aqueous phase is present. 6.3.5 Because both corrosion and microbiological activity may occur directly on the internal surfaces of a pipeline, the analysis of samples associated with surfaces may provide significant information. Whenever possible, a surface-associated sample should be collected in conjunction with each liquid sample collected. Surface-associated samples may be obtainable from the internal surface of the pipe section or component exposed to the pipeline fluids during operation. Coupons installed at or near a liquid sample location may provide surface-associated material for sampling. Generally, the volume of surfaceassociated material available for sampling is very small, unless the internal surface of the pipe section or component is fully accessible and significant deposits are present. Thus, collection and analysis procedures for small sample volumes of surface-associated materials must be anticipated and adjusted accordingly. 6.3.6 Samples should be collected from multiple locations on exposed surfaces, particularly when distinct differences in surface conditions are noted. The following should be considered and recorded for samples collected from exposed internal surfaces of pipe sections or components removed from service (see sample site inspection and testing checklist in Appendix A): 6.3.6.1 The location and distribution of solids, scales, deposits, or other materials visible on the walls of the pipe section or component being sampled, relative to the collected samples; 6.3.6.2 The characteristics of the surface-associated material: dry, moist, or wet; silt, sand; odor; color; texture, layering, or strata; at different locations on the internal surface of the pipe section or component relative to any samples collected; 6.3.6.3 The relationship of any corroded area to the sampled surface-associated materials; and 6.3.6.4 The physical location in the pipe section or component: clock position, relationship to damage observed in an internal coating; position of samples relative to disturbance, or contamination that occurred during handling of the pipe section or component sample. 6.3.7 Collecting samples for microbiological analysis should be avoided when the pipe section or component and coating have been extensively handled, exposed to atmosphere or sunlight for extended periods of time, or otherwise exposed to conditions where dehydration, temperature changes, or contamination could occur. If such samples are analyzed, the compromising conditions should be documented so they may be taken into consideration when a final evaluation of the data at that site is performed. 6.4 Sampling of Corrosion Products 6.4.1 Corrosion products or other materials that appear to be in physical contact with internal corrosion damage are samples of interest and should be collected for analysis, when present. Physical features of the deposits, for example, color (brown, black, white, or gray), shape (deposit, nodule, or film), texture, and odor, should be noted. 6.4.2 Corrosion products should be sampled for both microbiological and chemical testing. 6.4.3 The form of any visible corrosion: shapes, sizes, and depths of pits; crevice corrosion; underdeposit corrosion should be noted. (See figure 1).

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TM0212-2012

Figure 1: Examples of various pit morphologies as viewed in 17 cross section. 6.4.4 Any visible biological accumulations in corroded areas: form, color, texture, or odor (e.g., none, earth, rotten eggs) should be noted. 6.4.5 Many chemical characteristics of samples change immediately after collection; therefore, field testing should be performed as soon as possible after collection of samples. 6.5 Sampling of Biofilms 6.5.1 Attached microbes (sessile microorganisms) are normally the most important biological component of the bacterial ecology of an oilfield or natural gas system. Test data based on planktonic organisms are of limited value for assaying sessile microorganisms. Techniques for sessile microorganism study produce variable results. Consequently, few routine procedures can be described. However, Paragraphs 6.5.2 through 6.5.11 provide a basis for analytical work that yields valuable information about sessile microorganisms within an oilfield system. 6.5.2 Any removable field system component may be used to sample for sessile microorganisms. Standard corrosion coupons are a good example. Another alternative is the use of removed pipe sections (spools) or components. Alternatively, coupons designed for microbiological sample collection are available from corrosion monitoring system suppliers. Multiple disk coupons may be exposed in a side stream using a Robbins device or corrosion monitoring units. 6.5.3 Test coupons may be located in suitably designed side streams or placed within actual system flow paths by using properly designed coupons and access fittings. The coupons must be located such that they are representative of sessile microorganisms’ growth. For example, coupons are often located at the 6 o’clock position in oil and gas piping. 6.5.4 Metal coupons similar in composition to the pipeline should be used and the coupons should be electrically isolated to prevent galvanic effects.

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TM0212-2012 6.5.5 Sessile microorganism samples should be collected during any baseline or investigation survey. Good sources are filter backwashes, pig runs, pipe walls at unions, and similar locations where sessile microorganisms can grow. Corrosion failure areas should be tested for sessile microorganism populations. 6.5.6 The time required for development of a dense biofilm is variable and depends on multiple factors. A major obstacle in working with sessile microorganism samples is the uneven nature of sessile growth within the system (patchiness). For this reason, multiple sessile microorganism samples should be taken, or large surface areas should be sampled during each collection episode. 6.5.7 Sampling devices may be used to monitor biofilm development by periodically removing coupons and then applying techniques to count the microorganisms. Sessile microorganisms should be removed from the coupon by scraping with a sterile scalpel, swabbing, shaking with glass beads, or using ultrasonic devices. If scalpels or swabs are used, the biofilm and associated products should be completely dispersed using a vortex mixer with glass beads or by a sonic bath. In each case, sterile phosphate-buffered saline (PBS) solutions, or ultra-filtered field water, should be used to collect the removed microorganisms. The sample collection methods used should be effective and the assay methods used should allow efficient recovery of the microorganisms being analyzed. For sessile microorganisms in particular, the sample collection methods should be consistent during the course of an assay. Use of inconsistent sample collection and assay methods and contamination of samples are common threats to attaining meaningful trends in sessile microorganism data. 6.5.8 A consistent size of surface area from which surface samples are collected shall be maintained to produce repeatable, comparable results. 6.5.9 Biofilms, solids, and corrosion products from inside a pipeline may be collected from pigging residues for analysis; however, the results are not specific to any discrete portion of the pipeline segment being pigged. 6.5.10 PBS solutions used for sample collection, suspension, or temporary holding should have the chloride level of the buffer matched to that of the system conditions; otherwise cell membranes may be damaged. 6.5.11 Intact sections or panels may be cut out and sent for further inspection (both for chemical and microbiological investigation) when sections or components of a pipeline are taken out of service for maintenance and MIC is suspected to be involved in the corrosion taking place. Cold cutting methods should be used when possible to minimize alteration of the corrosion products and microorganisms inside the pipe. The metal sections or panels should be kept moist by sealing in a sterile plastic bag or similar container during transportation, and transportation time should be minimized. 6.6 Sampling Frequency 6.6.1 Sampling frequency depends on how the field system operates and should encompass the various stages of its operation. Some systems may exhibit large population variations over a short time. To establish the natural variation in microorganism numbers, samples (bulked or otherwise) should normally be taken over several days to establish a baseline. This work also should establish the sample locations that are representative of the system. An example of the sample frequency that might be required is twice-daily sampling for 3 to 5 days. In other cases, greater sample frequencies during longer time periods may be required. 6.6.2 System variables related to seasonal changes should be accounted for when the evaluation spans several months. Usually, these variables should only be established with extensive background monitoring. Initial frequency of sampling may also be based on system parameters. Guidelines on scoring various parameters to establish initial sampling frequency are available. Based on the analysis of the data, the frequency may be increased or 18,19 decreased. 6.6.3 During biocide treatments, additional samples should be taken immediately before treatment and at random intervals for a period of several days after each treatment. The sampling schedule used should be matched with the baseline sampling for the system. 6.6.4 To fully understand the ecology of a system, the entire system should be surveyed rather than only areas where elevated bacterial populations are expected or where obvious bacterial problems are occurring. 6.7 Sample Collection—Bulk Fluids

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TM0212-2012 6.7.1 Samples of bulk fluids from pipelines are often collected to quantify planktonic microorganisms levels and for identification. Microorganism testing data from bulk fluids should be used primarily for examination of trends and should be correlated with other data (such as liquid composition, operational conditions, sessile microorganism counts, and corrosion data) for proper interpretation. Collection and testing of bulk samples for internal MIC assessment should be performed with consideration of other data collected concurrently. 6.7.2 Natural microorganism population fluctuation and uneven microorganism distribution within pipeline systems may hamper accurate assessment of microorganism numbers. If baseline studies show a large variation in reported populations, several samples should be taken on each occasion and combined (bulked). However, this procedure may mask fluctuations in population profiles, if determining such profiles is a goal of the work. Bulk fluid samples may be collected in duplicate or triplicate to increase reliability in the test results. 6.7.3 Samples may be taken from flowing (e.g., pipeline) or static (e.g., storage tank) systems. Usually, samples should be obtained by cracking a valve and allowing the fluids to flow for several minutes (to thoroughly flush out dead-space fluids) before collecting the sample. In some instances (such as with tank bottoms or when sampling from open waters), a specially designed sampling apparatus (e.g., a sampling bomb, a sampling thief, or a pumped line) is required. When a hose, tubing, or other piping is used to extend the sample collection location any distance downstream from the sample origin within the pipeline system, the likelihood of erroneous or misleading microbial test results is increased significantly. Therefore, sample collection extension lines should be thoroughly flushed before actually collecting a sample and isolated from the atmosphere when not in use. 6.7.4 During sampling of systems containing both oil and water, phase separation should be permitted to occur before the water is used. Samples with low water cuts (i.e., low percentage of water) or those with tight emulsions may not contain enough water for testing. If an additional sample is necessary to obtain enough water for a particular test, caution should be exercised to prevent contamination during sample bulking. It is usually satisfactory to directly use an emulsion for microorganism isolation. The recorded water cut may also be used to estimate the water volume used in the culturing procedure. 6.7.5 Pigging residue sampling may be performed to collect bulk fluids or solids for microbial testing. Residues from maintenance or cleaning pigs typically contain films and deposits removed from the pipeline internal surface by the pig, and may contain unusually large numbers of microbes compared with routine bulk fluid analysis. Microbial enumeration results from pigging samples should not be overinterpreted considering the number and type of microorganisms may be highly variable. Sampling and analysis of pigging residues is one means of trending the efficacy of routine maintenance pigging and/or biocide treatments. Pigging residue samples may be collected from the pig itself, the pig receiver barrel, or the fluid envelope located just ahead of the pig. Fluid envelope samples are typically taken at frequent time intervals before the pig passes a sampling location, typically near the end of the pig run. Sample collection, preservation, and field testing procedures should be documented before the pig run. 6.8 Sample Collection—Internal Surfaces 6.8.1 A clean work surface should be used to avoid contaminating the inside of sample containers with dust or dirt from the work surface or general area when a sterile sample container is unsealed. The containers should be handled by gripping the lower part of the container. Skin contact with the upper part of the container must be avoided. 6.8.2 If a small volume of liquid is present, a sample should be taken using a sterile syringe or polyester-fiberfill swab. Both the liquid in the syringe and on the swab may be used for the enumeration of microorganisms as described in Section 7. The swab must be stored in a sterile plastic container until tested. 6.8.3 The pH of any liquid sample should be tested using pH paper (with a range of 1 to 14) or a pH meter with a microsensor electrode. A syringe or pipette should be used to extract a small amount of liquid to measure pH by putting a drop or two of liquid on the microsensor. If possible, pH measurements of any available solids in aqueous suspensions also should be attempted. 6.8.4 If surface deposits or corrosion products are present and adherent to the metal surface, they should be removed for sampling. Corrosion products may be collected by scraping the area with a sterile scalpel, or swabbing with a sterile polyester-fiberfill swab. 6.8.5 Multiple samples are typically taken from one or more of the following locations, when present: 6.8.5.1 Undisturbed liquids or solids immediately adjacent to the exposed internal pipeline steel surface or at an area of internal coating damage;

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TM0212-2012 6.8.5.2 Deposits associated with visual evidence of internal pipeline corrosion, especially those pit contents underneath nodules or tubercles that have been removed and are more likely to be uncontaminated. It should be noted when corrosion samples are known or suspected to be contaminated from outside sources; 6.8.5.3 Scale or biofilm on the internal steel pipeline surface or the backside of the internal coating; 6.8.5.4 Liquid trapped behind the internal coating or beneath scale or solids; 6.8.5.5 Other locations where the microorganisms’ activity is suspected. 6.8.6 Solid and liquid samples must be placed in clean, sterile, sealed, carefully labeled containers. The containers should be filled to no more than 60% maximum volume. The container must be sealed tightly, and the first container sealed again within a second container to reduce the risk of leakage. 6.8.7 Sample containers should be labeled with the sample location, sample origin, sampling date, and time, as well as the tests that have been performed on the sample. Extraneous dust, dirt, and debris shall not be introduced into the sample at the time of collection. The interior surfaces of sample containers or any other parts likely to be in direct contact with the sample must not have been handled directly. 6.9 Sample Transport 6.9.1 Changes in detectable numbers and types of microorganisms can occur rapidly after removal of samples from the environment. Personnel responsible for sample collection should arrive at the corrosion site with all solutions, media, and other necessary materials. If that is not possible, liquids and solids may be transported to a laboratory or other facility for processing and testing. The major challenge in transporting samples for microbiological evaluation is to ensure that microorganisms remain alive and active without multiplication. Sample collection may expose microorganisms to abrupt changes in pressure, temperature, atmosphere, and light, causing redistribution in numbers and types of microorganisms in the original sample. 6.9.2 After collection, samples should be stored in the dark away from temperature extremes. Liquid samples should be maintained at the original collection temperature by storing in an insulated container when transit times are less than 6 hours. If the sample has been collected from sources above 30 °C (86 °F), intrinsic heat can maintain the microbial population without significant changes. If the transit time is longer than 6 hours, the sample temperature should be lowered to less than 10 °C (50 °F) to restrict growth and competition. A standard method used to control postsampling shifts in microflora has been to provide a cold-temperature shock by packing ice packs around sample containers to bring the temperature down to within the range of 1 to 4 °C (34 to 39 °F), which reduces microbial activity to a basic survival metabolic mode. Prolonged storage for periods of longer than a few days can cause changes in the microflora and should be avoided.

_________________________________________________________________________ Section 7: Testing Guidelines 7.1 Field vs. Laboratory Testing 7.1.1 Bacteria, being living organisms, are highly sensitive to changes in their environment (e.g., temperature, salinity, and dissolved gases). Additionally, many chemical species associated with microbial metabolism, such as organic acids or sulfide compounds, can be rapidly oxidized or degraded. Thus, to obtain results that accurately represent pipeline conditions, certain tests relevant to MIC investigation or monitoring must be performed within minutes or hours of sample collection. Historically, this has been one of the factors that resulted in the lack of meaningful data for use in MIC assessment of pipelines. 7.1.2 As technology has improved, more types of tests and more sophisticated analyses have been made available for use in the field (i.e., near the point where samples are collected). Because indicators of the environmental conditions under which MIC may occur are readily degraded or lost after removal of a sample from the pipeline, a general rule for improving the quality of data is to perform testing on location whenever practical. Proper sample preservation and handling procedures must be followed diligently and consistently in cases in which testing cannot be performed in the field. 7.1.3 Results from both corrosion and microbiological tests should be integrated when evaluating the threat, likelihood, or presence of MIC. Information on both types of tests is provided in Section 7. Many of the test procedures described here are equally useful for evaluating external MIC.

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TM0212-2012 7.2 Microbiological Culture Testing 7.2.1 Although MIC is often attributed to a single type of microorganism, more often the corrosion is caused by the activities of several different organisms that form a community. Microbiological testing of pipelines has historically included testing for SRB, APB, general aerobic microorganisms, general anaerobic microorganisms, and in some cases, iron-depositing and iron-reducing bacteria. Iron-depositing and iron-reducing bacteria are difficult to grow in culture, and microscopic analysis is more commonly used for detection of these bacteria. 7.2.2 The objective of the microbiological culture techniques described in this standard is to approximate the size of the viable microorganism population in a solid or liquid sample using semi-quantitative estimates, or preferably, the most 20,21 probable number (MPN) method when sample replication is used. Such estimates are based on the assumption that microorganisms are normally distributed in liquids or solids. Microorganisms in solid and liquid environmental samples are usually enmeshed in particulates. Typically, a suspension of solid samples is made in a Ringer’s solution or phosphate buffer. Particles should be dispersed so colony-forming units are separated to maximize the accuracy of the estimate. Water samples should be mixed by shaking or stirring for 10 to 60 seconds just before dilution. 7.2.3 To culture microorganisms, a small amount of liquid or a suspension of a solid is added to a solution or solid that contains nutrients. The small sample is called an inoculum, and the nutrient is called the culture medium or growth medium. There normally are three considerations when growing microorganisms: type of culture medium, incubation temperature, and length of incubation. 7.2.4 The type of medium used to culture microorganisms determines to a large extent the numbers and types of microorganisms that grow. No culture medium can approximate the complexity of a natural environment. Under ideal 22 circumstances, liquid culture provides favorable growth conditions for 1 to 10% of the natural population. Typically, the presence of specific types of microorganisms is established, and a standard methodology is used so comparisons may be made. There are no “correct” culture media. A convenient method is to purchase prepared, premeasured, presterilized media. Test kits generally include syringes, swabs, and marking pens. Several culture media formulations for various 20 groups of microorganisms are included in NACE Standard TM0194. 7.2.5 Highly colored samples may sometimes interfere with culture interpretations. 7.3 Microscopy Methods—General 7.3.1 Microscopy is most commonly used to examine liquid or sludge samples directly to determine the overall numbers of microorganisms present without regard to their viability or species. Generally the procedure involves placing a few µL of sample on a glass slide, preparing the slide for examination using various staining techniques, and examining the slide with a light at magnifications from approximately 500X to 1,500X. Depending on the method of sample preparation, the detection 2 3 limit for all microorganisms present in a liquid sample, including viable, nonviable, and dead cells, is approximately 10 to 10 6 cells per mL. Levels of microorganisms in coastal seawaters are typically > 10 cells per mL. This procedure is typically performed in the laboratory. 7.3.2 Microorganisms structurally consist of lipids and proteins that degrade and break down once the cell dies, if the sample is not preserved after collection. Samples collected for microscopy are often preserved (fixed) using a formaldehyde or glutaraldehyde phosphate buffer solution. This type of preservation kills the microorganisms but preserves or fixes the structure of the cell. Fixative solution vials are commercially available. Typically only a few mL of the liquid or solid sample are preserved in the fixative. 7.3.3 One advantage of microscopy is that only a minute amount of sample is required for examination. A surface swab can provide adequate sample material (e.g., when no bulk liquid or solid is present). 7.4 Epifluorescent Microscopy 7.4.1 Epifluorescent microscopy involves treating the sample with a stain that fluoresces when viewed under a specific wavelength of ultraviolet light. This technique helps distinguish microorganisms from debris, or may be used to examine specific cellular structures of microorganisms. Hydrocarbons and some organic materials may interfere with epifluorescent microscopy as they give auto-fluorescence and obscure the signal from the biological material. This procedure is typically performed in the laboratory.

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TM0212-2012 7.4.2 Biological stains such as acridine orange (N,N,N',N'-tetramethylacridine-3,6-diamine), fluorescein isothiocyanate (FITC), and DAPI often are used for epifluorescent microscopy. A variety of microbiological test kits are commercially available. Acridine orange is a common nucleic acid stain that permeates cells to interact with DNA and RNA. 7.4.3 Fluorescent probes have been developed to “label” specific groups of microorganisms, or to distinguish live vs. dead cells in a sample. Fluorescent in situ hybridization (FISH) probes are used to identify and quantify certain species and groups of microorganisms. Because FISH labels only microorganisms with a certain content of ribosomal RNA, it is only active cells or cells that have recently been active that are enumerated. Quantitative use of FISH probes is discussed in Paragraph 7.8.2. 7.4.4 The DAPI method quantifies all intact microorganisms containing DNA (both living and inactive cells) in almost any 23,24 type of liquid sample. DAPI is often used in combination with FISH analysis, to help distinguish the total cell count from the number of cells that are labeled using the FISH probes. The information on total number of cells per mL of sample is valuable in cases in which growth of microorganisms in general has to be inspected and monitored over time. Further, based on previous data of total numbers of cells from many different systems, it is possible to evaluate whether the total number of cells is within a low, medium, or high range. The full DAPI method may be completed in less than half a day in a laboratory. The liquid sample is filtered whereby microorganisms (cells of bacteria, Archaea, and fungi) are collected on a filter. These are subsequently stained with a fluorescent dye that binds to the DNA in the cells and then washed to remove excess dye. Cells are manually counted in an epifluorescence microscope. Fluid samples should be fixed in the field with formaldehyde (36%) to a final concentration of 2% in the sample. Adequate sample amounts for this type of testing are 50 to 100 mL of fluid depending on the cell density. 7.4.5 Microscopy and biochemical methods have been used for many years, and genetic methods are now becoming available for the detection, quantification, and in some cases identification of microorganisms present at corrosion 25,26,27 sites. 7.5 Adenosine Triphosphate Photometry 7.5.1 Adenosine triphosphate (ATP), related to energy production and consumption, is present in all living cells. When cells die, however, ATP rapidly degrades. Consequently, the quantity of ATP in field samples is approximately proportional to the number of living microorganisms in that sample. ATP may give an indication of the viable biomass present in living organisms, and may be measured using an enzymatic reaction that generates light when ATP is present. The intensity of the light is measured in a photomultiplier, the output being proportional to the amount of ATP. 7.5.2 Several commercial field test kits are available for ATP quantification. Quantification of ATP typically relies on photometers that measure the amount of light emitted when the ATP within the sample is allowed to react with a particular enzyme. Before the reaction, the sample to be quantified is filtered and treated with gold buffers. These buffers assist in releasing the ATP from the organism so they can react with the enzyme. Finally, the sample and enzyme are combined and analyzed. Advantages of ATP measurement include speed to results (less than 10 min per sample), no underestimation of unculturable organisms, and use in any sample type including produced fluids, oil/emulsions, and solids. Often ATP measures should be backed up with at least one additional method for more specific quantification of the microorganism (e.g., SRB). 7.6 Hydrogenase Measurements 7.6.1 Hydrogenase is an enzyme produced by bacteria that use hydrogen as an energy source. Testing for the presence of the hydrogenase is one method used to enumerate bacteria populations in corrosion deposits and water samples in the field. 7.6.2 Quantification of bacteria populations using this method first involves extraction of the hydrogenase enzyme from the sample. The extracted enzyme is preserved in a solution that maintains enzyme activity and then placed within a reaction chamber where hydrogen is introduced. The hydrogen is oxidized and a redox indicator color change reveals the presence of the hydrogenase enzyme (refer to NACE Standard TM0194). The reaction typically is not rapid; it can take anywhere from 30 minutes to 4 hours. The reaction time and developed color intensity together are used to measure the relative activity of the enzyme. 7.7 Adenosine Phosphosulfate Reductase 7.7.1 Adenosine phosphosulfate (APS) reductase is an enzyme specifically associated with SRB. Thus measurement of the APS reductase present in a bacterial sample provides an indication of the active SRB concentration. Detection and measurement are based on immunological methods and may be performed using a field kit.

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TM0212-2012 7.7.2 The test involves exposure of the sample to small particles containing antibodies. These particles specifically capture the APS reductase enzyme. The particles, now mixed with APS reductase, are subsequently isolated on a porous membrane and exposed to specific indicator chemicals. Reaction between the particles and chemicals results in a color change that is proportional to the concentration of the APS reductase in the sample. 7.8 Molecular Microbiological Methods 7.8.1 Molecular microbiological methods (MMMs), also referred to as genetic methods, are culture-independent approaches that provide direct analysis of samples without the bias introduced by the growth process used during culturing. Because no prior growth of microorganisms is required, MMMs accept very small amounts of any type of sample (liquid, biofilm, solid, and dry) with or without live bacteria. After genetic materials are extracted from the sample, assays that are very specific and 28,29 render a more precise quantification of various types of bacteria than culture tests are performed in the laboratory. A comparison of MMMs is shown in Table 1 and Figure 2.

Table 1 23 Comparison of Molecular Microbiological Methods Method (MMM)

Method Based On

Living Cells Counted?

Dead Cells Counted?

Quantitative Method?

DAPI

Microscopy

Yes

Yes

Yes

Total cell counts (live and dead)

Information Yielded

FISH

Microscopy

Yes

No

Yes

Total numbers of live bacteria Total numbers of live Archaea Total numbers of live SRB Total numbers of live SRA

DGGE

PCR

Yes

Yes

No

Comparison of populations Identification of abundant microorganisms

Yes

Numbers of total bacteria Numbers of total Archaea Numbers of SRB Numbers of SRA 3 Numbers of three groups of methanogens

qPCR

PCR

Yes

Yes

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TM0212-2012

Figure 2: An illustration of the portions of the different pools of microorganisms (live, inactive, and dead) typically present in samples from the oil industry that are enumerated using various MMMs compared to the MPN (culturing) method. Each of 29 the methods indicated is discussed further in the text.

7.8.2 Quantitative FISH—quantitative FISH is a MMM in which only living and active cells are stained with a fluorescent dye visible during epifluorescence microscopy. Unlike the DAPI method, FISH probes may be designed to attach only to selected groups of microorganisms (e.g., specific types of SRB or SRA). Therefore, only the specific target microorganisms are visible and may be enumerated during subsequent microscopy. The quantitative FISH method does not underestimate organisms that do not grow in culture. FISH is a microscopy method that uses synthetic oligonucleotides (synthetic DNA) tagged with a fluorescent molecule (dye). Together, the synthetic DNA and the fluorescent molecule are referred to as a probe. The probe is mixed with the bacteria in a fluid sample and the numbers of bacteria (or Archaea) that take up the probe and have it hybridize to their rRNA are counted. The quantitative FISH method differentiates active/alive microorganisms from dead microorganisms. A probe may be designed to detect a general population (e.g., total bacteria or total Archaea) or a specific genus or species (e.g., desulfovibrio desulfuricans). Often a given sample is analyzed using several different probes to understand the prokaryotic diversity in a sample, and which types/species of microorganisms are most abundant. The preparation steps for the quantitative FISH method are different from the DAPI method. However, cells stained for the quantitative FISH method are counted in the same manner as in direct bacterial counts (for the DAPI method) in the laboratory. Adequate sample amounts for this type of testing are in the range of 50 to 100 mL of fluid depending on the cell density. Samples are filtered onto 0.2 μm filters. FISH probes are selected to target total bacteria and Archaea, as well as specific groups of relevance (e.g., SRB). Typically the samples are inspected by epifluorescence microscopy at 1,000X magnification. The cells stained with each probe are counted and related to the overall number of cells obtained by the DAPI method (see Paragraph 7.4.4). 7.8.3 qPCR—PCR and qPCR is a MMM to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating millions of copies of a particular DNA sequence. The qPCR is an emerging method for enumerating microorganisms in complex environmental samples, particularly in solid samples where epifluorescence microscopy (used for the DAPI method and FISH method) may be difficult to perform because of background interference. The qPCR method enumerates genes rather than individual cells by applying a modified polymerase chain reaction (PCR) method. Like the quantitative FISH method, the qPCR method may be applied to count total cells or specific groups of microorganisms (e.g., 4,9,30,31 SRP or methanogenic Archaea). Because qPCR targets the DNA in all prokaryotes, the qPCR method measures living, inactive, and dead microorganisms. qPCR may be used to quantify the total number of microorganisms or a specific genus/species of microorganisms in nearly any type of sample, including produced fluids, oil/emulsion, and solids. The qPCR method does not underestimate organisms that do not grow in culture. qPCR may be done on both fluid and solid samples as well as microorganisms collected via membrane filtration. qPCR uses synthetic DNA (called primers) tagged with a fluorescent molecule or synthetic DNA mixed with a DNA intercalating agent (dye) to quantify organisms using a modified

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TM0212-2012 version of the PCR method. Briefly, total prokaryotic DNA is extracted and amplified using primers that target to a conserved region of the bacterial DNA. The region used may make the assay very general (meaning counting total bacteria or Archaea), or very specific (meaning counting a single genus or specie). Similar to quantitative FISH, the qPCR method may be used to enumerate a very general group of bacteria (i.e., total bacteria or Archaea) or very specific organism (e.g., desulfovibrio desulfuricans). Adequate sample amounts for this type of testing are 50 mL of fluid, 2 to 5 g of solid, or a 0.2 or 0.45 μm filter with a minimum of 10 mL of fluid passed through it. 7.8.4 DGGE—Denaturing gradient gel electrophoresis (DGGE) is a MMM based on the PCR method that is used for comparing microbial communities across a number of different samples. During DGGE, genetic material in individual samples is amplified by PCR and subsequently compared by electrophoresis. DGGE is used for identifying dominant groups of microorganisms in individual samples and for evaluating how the microorganisms are distributed between 4,19,23,32,33 samples. DGGE may be performed on any fluid or solid sample, as well as bacteria collected via membrane filtration. Adequate sample amounts for this type of testing are 50 mL of fluid, 2 to 5 g of solid, or a 0.2 or 0.45 μm filter with a minimum of 10 mL of fluid passed through it. 7.9 Organic Acids Organic acids such as butyric, pyruvic, propionic, and acetic acid are by-products or intermediary species of microbial metabolism. Gas chromatography-mass spectrometry (GC-MS) or high-pressure liquid chromatography (HPLC) is used in the laboratory to identify and quantify organic acid species in properly preserved samples. Organic acids quickly degrade; therefore, samples are preserved by filtration into nitrogen-purged vials and maintained at 4 °C (40 °F) until analysis is performed. 7.10 Chemical Analysis 7.10.1 Corrosion products may be taken from the steel surface, coating, or optimally, from the pit contents underneath a deposit that has been removed. The color and type of sample collected should be noted in each case. Although liquid or corrosion product samples are often limited in volume, when sampled from corroded pipe, on-site tests should be performed because significant chemical changes can occur during a short period of time. Additionally, compositional analyses (i.e., anions, cations/metals, and organic acids) should be performed in the laboratory. 7.10.2 Field tests on liquids should include pH, total alkalinity, and dissolved hydrogen sulfide. Field tests on solids and corrosion products in aqueous suspensions should include pH and a qualitative analysis for the presence of sulfides and carbonates. Carbonates are present if noticeable bubbling occurs when a drop of dilute hydrochloric acid is placed on a small portion of the corrosion product. Sulfides may be detected by the characteristic odor of rotten eggs, or by exposing the acid-treated corrosion product to lead-acetate test paper. A white-to-brown color change occurs in the presence of sulfides. Follow-up testing in the laboratory with more sophisticated analytical equipment (e.g., energy dispersive spectroscopy [EDS], x-ray diffraction [XRD], Raman spectroscopy) to determine the elemental and mineral phases present should be performed to verify field tests. 7.11 Pipeline Examination 7.11.1 When examining internal surfaces of the exposed pipeline, disbonded coating, corrosion products, and other materials should be removed from the internal wall using a clean spatula or knife, with care taken not to scratch the metal. Any remaining material should be removed with a clean, dry, stiff brush (e.g., nylon bristle brush). A brush with metal bristles obscures the pit features. In cases when all of the material cannot be removed with this method, a brass bristle brush may be used in the longitudinal direction. The area subsequently may be cleaned with an air blast or an alcohol swab. A shiny metallic surface in the pit suggests the possibility of active corrosion. However, judgment should be used to differentiate this condition from one created by scraping the steel surface with a metallic object, such as the knife or spatula used to clean the surface, or to obtain the sample. 7.11.2 The steel surface shall be inspected for corrosion, and any damage shall be carefully documented. When possible, gauges should be used to measure the pit depths. Also, the length of the corroded area in relation to the circumferential and longitudinal position should be determined. The newly cleaned corroded area should first be examined without magnification. Then, a low-power magnifying lens at 5X to 50X power should be used to examine the detail of the corrosion pits. An example checklist is provided in Appendix A. 7.12 Analysis of Pipeline Samples 7.12.1 Careful analysis of pipeline samples (pipe sections or components that have been removed from service) may provide useful information regarding internal corrosion mechanisms.

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TM0212-2012 7.12.2 Precautions should be taken to avoid contamination of the internal surfaces of the pipeline before, during, and after the pipe section or component is removed from service. If inadvertent alteration of the internal surface of the pipeline sample occurs, the nature of the alteration should be noted to aid in correct interpretation of subsequent testing results. 7.12.3 Alteration of pipeline samples can occur as a result of removal efforts, exposing the surface deposits to oxygen, foreign matter, temperature changes, and contamination from handling. 7.12.4 Generally, samples should be collected immediately after the pipe section or component is removed from service (i.e., within minutes when possible). Corrosion products and biofilms can change profoundly on exposure to air, affecting test results. 7.12.5 When samples cannot be collected immediately after a pipe section or component is removed, the internal surfaces and deposits may be covered temporarily with new, clean, plastic sheeting to minimize exposure to air until samples are collected. This practice may compromise the condition of the surface samples to an unknown extent, and should be used only when samples cannot be collected immediately. 7.12.6 Culture tests of samples from pipe that has been exposed to air, dehydration, and potential contamination for extended periods of time (i.e., days) should not be relied on for providing useful data. 7.12.7 The internal condition of pipeline samples at the time of removal should be carefully and thoroughly documented; these data are important in the interpretation of both field and laboratory tests. An example checklist is provided in Appendix A. 7.12.8 Field and laboratory tests of pipeline samples for internal corrosion analysis should be directed toward characterization of the biological, chemical, and metallurgical conditions present in the pipeline. In particular, distinction should be made between samples collected in corroded areas vs. areas where no corrosion is present. 7.12.9 Corrosion features on the pipeline sample should be protected from further corrosion after removal of the pipeline sample. Microscopic features of corrosion damage are easily lost because of oxidation or improper handling. 7.12.10 Optical microscopy and scanning electron microscopy (SEM) of internal corrosion features may provide useful information regarding the origin and growth of localized corrosion. 7.12.11 Metallographic examination of corroded areas removed from pipeline samples may provide information about the nature of the corrosion relative to the microstructure of the pipeline. Particularly, selective or preferential corrosion of microstructural features may be determined from metallographic examination. 7.12.12 Chemical analysis of microscopic corrosion features using energy dispersive spectroscopy (EDS) or other microanalytical techniques may provide useful data regarding localized corrosion initiation mechanisms. 7.12.13 Preservation methods, such as in situ histological embedment of biofilms and corrosion products, may yield samples suitable for microscopic examination using fluorescent staining techniques, phase contrast examination of thin sections, and transmission electron microscopy (TEM). 7.12.14 Interpretation of data collected from pipeline samples should be performed as described in Section 8. 7.13 Data and Records Management All data and information (e.g., sample collection method used) should be documented on field data sheets or in logbooks with permanent ink.

_________________________________________________________________________ Section 8: Corrosion Monitoring 8.1 General 8.1.1 MIC cannot be evaluated, assayed, or diagnosed solely with microbiological data and vice versa. Corrosion data should be collected and integrated with microbiological results to distinguish MIC from other corrosion mechanisms.

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TM0212-2012 8.1.2 Corrosion monitoring data should be collected at the same locations as microbiological test data, whenever possible. When corrosion monitoring and microbiological monitoring are performed at different locations on a pipeline, the relationship between the two test locations should be identified (e.g., upstream, downstream, similar operating conditions). 8.2 Conventional Coupon Monitoring 8.2.1 Monitoring the corrosiveness of pipeline contents may be performed using coupons that are inserted into the pipeline at locations where corrosion is a potential threat. Conventional coupons (weight loss coupons) may be exposed for approximately 6 months, then removed from the pipeline and analyzed. Analysis should consist of cleaning, weighing to determine mass loss, and examination for pitting and mechanical damage. NACE Standard RP0775 provides details 34 regarding the use of coupon monitoring and analytical procedures. ASTM Standard G46 covers the selection of procedures 35 that can be used in the identification and examination of pits and in the evaluation of pitting. 8.2.2 Corrosion coupons are particularly useful when general corrosion is a threat. Macroscopic isolated pitting corrosion, particularly as related to crevices formed by deposits or films, may be more difficult to reliably detect with corrosion coupons. The initiation and growth of individual MIC pits may be arbitrary, and the coupon represents a relatively small area compared to the entire pipeline. The location and position of coupons in the pipeline system affects the type and severity of corrosion 36 experienced by the coupons. 8.3 Extended-Analysis Coupons 8.3.1 The extended-analysis coupon is similar to a mass-loss coupon in many ways. In fact, all the parameters measured using a mass-loss coupon may be assessed using the extended-analysis coupon. However, the differences are in the purpose of the evaluation, the level of care in handling, the length of exposure period, and the extent of the evaluation performed. Extended-analysis coupons have been used to assess corrosion mechanisms in pipeline systems and help 37,38,39 determine effective mitigation strategies. 8.3.2 Extended-analysis coupons should be manufactured with a specific surface finish to facilitate microbiological attachment and provide a consistent reference pattern for analyses at high magnification. 8.3.3 In general, the exposure period for extended-analysis coupons should be shorter than that for mass-loss coupons, with the intended purpose of capturing the initiation events of corrosion. Differentiation between electrochemical and microbiological corrosion initiation allows the user to determine and refine treatment regimens based on physical evidence. 8.3.4 Corrosion evidence, including solids and microorganisms, may be preserved for later examination using replication techniques. The corrosion evidence also should be maintained spatially compared to the physical coupon, allowing direct correlation between corrosion materials and the coupon surface. 8.3.5 The primary purpose of using an extended-analysis coupon, as opposed to a mass-loss coupon, is to determine the initiation mechanism involved in the corrosion process. Extended-analysis coupons enable differentiation of electrochemical 40,41 corrosion vs. microbiological pitting. Generally, the extended-analysis coupon should be installed in an area that would represent worst-case corrosion in the process flow. 8.3.6 From manufacturing and installation, through exposure and removal, to laboratory evaluation, the extended-analysis coupons shall be handled with specific care to preserve the corroded surface in the same condition it was when removed from the process stream. 8.3.7 To identify the initiation mechanism, exposure periods should generally be 15 to 90 days, but may be customized based on results obtained from any given process stream. 8.3.8 After exposure, the coupons should be shipped within 24 hours in a cooled environment and in a controlled, noncorrosive, abiotic, sterile shipping media solution to a laboratory experienced in this type of analysis. 8.3.9 The evaluation should begin with careful preparation of coupons that minimizes disturbance of the coupon surface. Upon receipt of the coupons, the laboratory should preserve the corrosion environment on the coupon by following methods designed to minimize corrosion and preserve any microbiological evidence. The last step of this process involves embedding the coupon and attached corrosion products in an acrylic resin for microbiological and elemental analysis. This hardened acrylic embedment is referred to as a replica. The replica should be carefully removed from the coupon and stored for later analysis. The coupon surface should be carefully cleaned using cotton swabs wetted with a solvent (typically acetone). When all the acrylic material is removed, the coupon may be used for mass-loss determination, as well as optical microscopy and SEM evaluation.

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TM0212-2012 8.3.10 Optical microscopy evaluation should consist of both qualitative and quantitative assessments that identify the condition of the coupon surface at magnifications up to 40X. Qualitative assessments should include identifying the corrosion as etching or pitting and providing a relative assessment of severity. Quantitative assessments should include measuring maximum pit depths/widths, as well as number of pits per unit area. 8.3.11 SEM and EDS may be used to qualitatively assess the coupon surface at high magnifications, typically up to 2,000X. Because the difference in the appearance of corrosion can be extreme at different magnifications, the SEM evaluation should be performed independent of the optical microscopy evaluation. The corrosion should be identified as etching or pitting and a relative assessment of severity should be provided. Based on microscopic pit size, shape, distribution, and morphology, the SEM examination also may facilitate differentiation between abiotic and biotic pit initiation. Other surface features may be identified as well, including micromechanical damage caused by particulate in the process stream impacting the coupon surface, as well as the presence, type, and extent of scale. EDS may be used to identify the elemental composition of embedded particles or scale. 8.3.12 Evaluation of the replica may be performed using epifluorescent microscopy (microbiological) and EDS (elemental). The purpose of epifluorescent microscopy is to determine the presence of microorganisms and quantify the number of microorganisms observed. The purpose of the EDS evaluation is to identify the elemental composition of any scale or debris that is present in the replica. The orientation of material in the replica in relation to the coupon surface should be preserved as well, which allows the analyst to compare the replica evidence directly to the exposed coupon surface for a direct correlation. 8.3.13 Extended-analysis coupons may be used to evaluate MIC initiation in laboratory flow loops with microbial consortia 42 43,44 from field environments. Guidelines for bench-top MIC testing have been published by Eckert, et al. 8.4 Corrosion Monitoring Probes 8.4.1 Internal corrosiveness monitoring may be performed using a variety of corrosion probes, including electrical resistance (ER), linear polarization resistance (LPR), electrochemical potential noise (EPN), and galvanic. NACE Publication 3T199 45 should be used as a reference when considering the use of corrosion probes for monitoring corrosion rates in pipeline systems. 8.4.2 Because MIC is most commonly manifested as pitting damage, detecting the initiation and growth of pitting (particularly as associated with microbial activity) on the internal surface of the pipeline should be considered when using corrosion probes. Some types of corrosion probes (e.g., ER) do not detect pitting, or poorly distinguish general corrosion from pitting. As for all monitoring techniques, data from corrosion probes should be interpreted in conjunction with other microbiological, operational, and corrosion data about the pipeline. 8.4.3 Biofilm growth on a metal surface immersed in conductive media can affect electrical properties (e.g., impedance, open-circuit potential) if the metal is placed in an electrical circuit, such as in a corrosion probe. Changes in electrical properties as a result of biofilm growth are monitored with some commercially available corrosion probes. A four-electrode 46,47,48 probe for simultaneously monitoring SRB activity and corrosion rate has been described. 8.5 Inspection Techniques 8.5.1 Inspection data are commonly used to detect and monitor corrosion-related damage. Techniques generally include visual inspection, ultrasonic testing (UT), radiographic testing (RT), and magnetic flux methods. Inspection may be used for establishing the orientation, distribution, density, size, shape, and extent of internal corrosion damage; however, inspection results alone do not establish the presence of MIC. Inspection data should be integrated with other information about the internal environment of the pipeline. 8.5.2 Section 3 of NACE Publication 3T199 discusses direct, nonintrusive corrosion monitoring techniques, and provides a frame of reference for selection and application of inspection techniques for internal corrosion monitoring. 8.5.3 The results of in-line inspection (ILI) may provide information about the location and severity of internal corrosion relative to inputs and outputs of a pipeline, operating parameters, design, elevation, and other considerations. ILI data may be used to identify sample locations for microbiological and chemical testing of pipeline fluids.

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TM0212-2012 8.5.4 Internal corrosion direct assessment (ICDA) standards have been published for normally dry gas pipelines (DG49 50 ICDA) in NACE SP0206, for liquid petroleum pipelines (LP-ICDA) in NACE SP0208, and for wet gas pipelines (WG-ICDA) 51 in NACE SP0110. As for ILI data, ICDA methods provide information about the location and severity of internal corrosion relative to pipeline design and operating conditions. ICDA information may be useful for guiding MIC monitoring and mitigation activities. 8.6 Operating Parameters 8.6.1 Operating parameters for a pipeline may be monitored using online and offline techniques. Information regarding operating parameters is valuable for integration of corrosion and microbiological monitoring data. As with most data related to MIC assessment, longer-term operating parameter trends rather than one or a few data points should be examined. 8.6.2 Selection of online and offline monitoring techniques must consider the reliability of the data, the cost of the equipment or test, maintenance and safety, and other benefits and limitations. Operating parameter data produced by any technique should be assessed for factors that can affect the results. 8.6.3 Some of the parameters that may be measured online include pH, conductivity, dissolved oxygen, redox potential, fluid velocity, pressure, temperature, dew point, and deposit accumulation/fouling. 8.6.4 Examples of operating parameters that may be measured offline include alkalinity, metal ion composition/content, anion composition/content, dissolved gas or gaseous phase analysis, total dissolved solids (TDS), total suspended solids (TSS), inhibitor/biocide residuals, total acid number (TAN), sulfur, nitrogen, and carbon content.

________________________________________________________________________________ Section 9: Application of Test Methods to Pipelines and Interpretation of Data 9.1 Data Interpretation 9.1.1 Because microorganisms are ubiquitous, the presence of bacteria or other microorganisms does not necessarily indicate a causal relationship with internal corrosion observed in a pipeline. In fact, microorganisms may nearly always be cultured from natural environments. Therefore, merely detecting viable microorganisms in liquid or solid samples associated with internal corrosion does not necessarily prove that MIC has occurred. 9.1.2 For any given sample, the actual number of microorganisms determined by any analytical technique is far less significant than trends that may be observed among samples from a series of locations or within a period of time. This point is particularly important relative to analysis of results from bulk fluid samples. 9.1.3 To determine the cause of, or potential for, internal corrosion all chemical, microbiological, metallurgical, and operational data about the pipeline must be examined, integrated, and analyzed. Analytical results from samples obtained in the corroded area should be compared with the results from reference samples taken outside the corroded area. 9.1.4 To determine the presence of internal MIC in a pipeline, microbiological, operational, and chemical data must be integrated. Analysis of the data should demonstrate that microorganisms and their activities provide the predominant influence over the corrosion mechanism present in the pipeline, as opposed to abiotic mechanisms. 9.1.5 Data in support of diagnosis for internal MIC may be collected for a variety of purposes including system assays, routine monitoring, monitoring in support of mitigation activities, and corrosion damage investigation. 9.1.6 Pipeline operators may collect data in support of internal MIC analysis in conjunction with other routine sampling, maintenance, integrity assessment, inspection, and environmental and regulatory compliance activities. 9.1.7 Interpretation of data relative to the assessment or determination of MIC in a pipeline should consider a number of factors that can influence both corrosion and microorganism growth, including water cut, velocity, liquid composition, temperature, pressure, and biocide or inhibitor treatment. 9.1.8 Interpretation of data related to bulk phase (macro scale) conditions must be done in consideration of the fact that microorganisms can exist and flourish in microniches. For example, pipelines may experience little or no corrosion damage as a result of a wide range of conditions throughout the majority of the pipeline, yet be affected by MIC in a small area of a specific section or component of the pipeline because of the unique environment present only at that location.

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TM0212-2012 9.1.9 Because MIC is a complex mechanism that involves electrochemistry, microbiology, corrosion control, pipeline operation and design, and engineering and integrity assessment, plans to evaluate MIC of pipelines and analyze data should include input from those with expertise in the respective fields. Pipeline operators should seek input from a multidisciplinary team whenever possible, so as not to emphasize one aspect of science or technology over another. 19, 52, 53

9.1.10 Risk and mechanistic models also can be used as guidelines to interpret the data. 9.2 System Assay

9.2.1 A system assay may be performed to assess the internal corrosion threat of MIC in a pipeline system. 9.2.2 Table B1 in Appendix B provides examples of background data that may be collected before, or as part of, a system assay for the threat of MIC. The purpose of a comprehensive data review is to determine the cause and location of conditions that exhibit the potential for internal corrosion and MIC in particular, and to identify areas where more information is required. Collecting, reviewing, and analyzing information regarding the current and historical operating conditions and design of the 51 pipeline being assayed should be performed to conduct a reliable system assay for the threat of MIC. 9.2.3 The type, number, and locations of additional tests determined to be useful in assaying the MIC threat for a pipeline system should be identified after the initial comprehensive data review. The specific purpose of each additional test should be identified in regard to how the results are intended to be used to improve the confidence level of the assay. The particular types, numbers, and locations of additional tests selected should take into account the advantages and limitations of each technique. Generally, microbiological, chemical, and corrosion testing as part of a system assay should seek to establish trends in the course of a period of time. Environmental differences between bulk fluid phase and surface films should be considered during the selection of tests, and when performing the tests and interpreting test results. 9.2.4 In many pipeline systems, the potential for multiple and/or concurrent corrosion mechanisms exists. The results of a system assay should be used to distinguish the significance of the threat for MIC in comparison with the threat for other potential internal corrosion mechanisms in the pipeline system. For example, the assay of a pipeline system with the threats of underdeposit concentration cell corrosion and MIC should establish the relative contribution of each threat mechanism so an appropriate mitigation response can be identified. The results of a system assay may be used to identify follow-on mitigation and monitoring activities. 9.3 Routine Monitoring 9.3.1 Routine monitoring may be performed to evaluate the internal corrosion threat of MIC and/or monitor the effects of mitigation measures taken to control MIC and other corrosion mechanisms in a pipeline system. Generally, the principles described for a system assay in Paragraph 9.2 should be applied before (or as a part of) identifying and adopting routine monitoring. 9.3.2 Baseline data for the tests to be performed should be collected at the beginning of a routine monitoring program. Operating condition data should be closely monitored in conjunction with internal corrosion and microbiological data. Normal and episodic operating conditions often profoundly affect the results of corrosion and microbiological tests; therefore, these data should be integrated for analysis. 9.3.3 The type, number, and locations of tests determined useful in monitoring the MIC threat for a pipeline system should be identified after an initial comprehensive data review. The specific purpose of each additional test should be identified in regard to how the results are intended to be used to improve the confidence level of the overall results. The particular types, numbers, and locations of additional tests selected should take into account the advantages and limitations of each technique. Generally, microbiological, chemical, and corrosion testing as part of routine monitoring should seek to establish trends over a period of time. 9.3.4 Consistent techniques, methods, procedures, materials, and sample handling must be used. Because routine monitoring may be used to identify trends and normal variations in pipeline system chemistry and microbiology, the effects of improper sample handling or field testing could provide misleading results. 9.3.5 When the potential for multiple and/or concurrent corrosion mechanisms exists, the results of routine monitoring tests should be used to distinguish the significance of the threat for MIC in comparison with the threat of any other potential internal corrosion mechanisms in the pipeline. Ultimately the objective of routine monitoring is to identify and measure actions taken to reduce internal corrosion; the results of monitoring should demonstrate improvements in corrosion control and reduced corrosion damage to the pipeline system.

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TM0212-2012 9.3.6 The results of routine monitoring tests may be used to provide continuous feedback to mitigation efforts such as process improvements, fluid quality improvements, application of corrosion inhibitor or biocide, and maintenance pigging programs. 9.4 Corrosion Damage Investigation 9.4.1 Generally, MIC is suggested by increased levels of viable microorganisms associated with pit areas that were uncontaminated by adjacent liquids or solids, or microscopic determination of iron and manganese bacteria in corrosion deposits. These are often good indicators of microbial involvement. 9.4.2 To validate MIC as the cause of internal corrosion, the following three conditions must be met: 9.4.2.1 Condition 1—Assuming there is no known or suspected contamination from outside sources, demonstration of increased levels of specific types of viable microorganisms (bacteria or fungi) associated with the corrosion, relative to samples taken outside the corroded area; 9.4.2.2 Condition 2—Chemical indicators that support the microbiological evidence (e.g., elevated levels of sulfide or sulfur in pit deposits for SRB and SRA, or organic acids for APB) are identified in the corroded area; and 9.4.2.3 Condition 3—Biotic factors (the presence or activities of living organisms) are identified as the primary contributor to the corrosion damage. The objective of this verification step is to establish that the presence of specific biotic conditions was the predominant contributor to the corrosion observed. The influence of abiotic factors (chemical or physical conditions unrelated to living organisms) on the corrosion mechanism also must be considered in all cases. The nature of the corrosion damage to the pipeline system should be consistent with the nature of the identified microorganism(s) and their by-products, or their physical influence on the formation of corrosion cells. For example, if viable APB or methanogens are concentrated at the corrosion damage relative to the environment, and evidence of their metabolic activity (organic acids) is determined to be associated with the corrosion, the nature of the corrosion damage should be consistent with these observations (e.g., accelerated corrosion damage or pitting beneath the biofilms). This is an important step in the final diagnosis because it is often difficult to discern between the relative contributions of various factors (biotic and abiotic) affecting localized corrosion. 9.5 Corrosion Mitigation 9.5.1 The methods described in this standard may be used to determine the need for, and effectiveness of, mitigation measures for controlling MIC. Specific procedures for mitigating MIC of pipelines are beyond the scope of this standard. 54

9.5.2 NACE SP0106 provides general information about methods for controlling MIC by design, operation, and specific measures, such as maintenance pigging and biocide treatment. 9.5.3 Many of the mitigation measures used to control internal corrosion of pipelines may be effective for both biotic and abiotic corrosion mechanisms. For example, cleaning pigs can break up deposits that promote crevice corrosion, as well as disrupt biofilms related to MIC. 9.5.4 Simply reducing the numbers of viable microorganisms in a pipeline system (e.g., with biocide treatment) should not be equated with controlling internal corrosion in the pipeline system.

_________________________________________________________________________ References 1. B.J. Little, P. Wagner, “Microbiologically Influenced Corrosion,” in Peabody’s Control of Pipeline Corrosion, 2nd ed., R.L. Bianchetti, ed. (Houston, TX: NACE, 2001). 2. NACE/ASTM G193 (latest revision), “Standard Terminology and Acronyms Relating to Corrosion” (Houston, TX: NACE, and West Conshohocken, PA: ASTM). 3. H.P. Klenk, et al, “The Complete Genome Sequence of the Hyperthermophilic, Sulphate-reducing Archaeon Archaeoglobus Fulgidus,” Nature 390 (November 1997): pp. 364-370.

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TM0212-2012 4. J. Larsen, et al, “Consortia of MIC Bacteria and Archaea Causing Pitting Corrosion in Top Side Oil Production Facilities,” CORROSION/2010, paper no. 10252 (Houston, TX: NACE, 2010). 5. B.J. Little, et al., “Impact of Biofilms on the Electrochemical Behavior of Stainless Steels in Natural Seawater,” J. Biofouling 3, 45 (1991). 6. T.L. Skovhus, K.B. Sørensen, J. Larsen, K. Rasmusssen, M. Jensen, “Rapid Determination of MIC in Oil Production Facilities with a DNA-based Diagnostic Kit,” SPE International Conference on Oilfield Corrosion, paper no. SPE 130744 (Aberdeen, UK: SPE International, 2010). 7. S. Papavinasam, A. Doiron, R.W. Revie, “Effect of Surface Layers on the Initiation of Internal Pitting Corrosion in Oil and Gas Pipelines,” CORROSION 65, 663 (2009): pp. 663-673. 8. S.D. Papavinasam, O. Omotoso, K. Michaelian, R.W. Revie, “Effect of Field Operational Variables on the Propagation of Internal Pitting Corrosion of Oil and Gas Pipelines,” CORROSION 65, 11 (2009): pp. 741-747. 9. J.A. Hardy, J.L. Brown, “The Corrosion of Mild Steel by Biogenic Sulfide Films Exposed to Air,” CORROSION 40, 12 (1984): p. 650. 10. T.R. Jack, M.J. Wilmott, R.L. Sutherby, R.G. Worthingham, “External Corrosion of Line Pipe—A Summary of Research Activities,” MP 35, 3 (1996): p. 18. 11. K. Sørensen, J. Larsen, T.L. Skovhus, B. Højris, “Significance of Troublesome Sulfate-Reducing Prokaryotes (SRP) in Oilfield Systems,” CORROSION/2009, paper no. 09389 (Houston, TX: NACE, 2009). 12. D.H. Pope, T.P. Zintel, A.K. Kuruvilla, O.W. Siebert, “Organic Acid Corrosion of Carbon Steel: A Mechanism of Microbiologically Influenced Corrosion,” CORROSION/88, paper no. 88079 (Houston, TX: NACE, 1988). 13. T.R. Jack, B. Rogoz, B. Bramhill, P.R. Roberge, “The Characterization of Sulfate-Reducing Bacteria in Heavy Oil Waterflood Operation,” in Microbiologically Influenced Corrosion Testing, K.R. Kearns, B.J. Little, eds. (West Conshohocken, PA: ASTM, 1994), p. 108. 14. M. Davies, P.J.B. Scott, Oilfield Water Technology (Houston, TX: NACE, 2006), pp. 213-242. 15. I.B. Beech, J. Sunner, “Biocorrosion: towards understanding interactions between biofilms and metals,” Current Opinion in Biotechnology 15 (2004): pp. 181-186. 16. NACE Standard TM0106 (latest revision), “Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion (MIC) on External Surfaces of Buried Pipelines” (Houston, TX: NACE). 17. R.B. Eckert, Field Guide for Investigating Internal Corrosion of Pipelines (Houston, TX: NACE, 2003). 18. S. Papavinasam, R.W. Revie, R.D. Sooknah, M. de Romero, “Modeling the Occurrence of Microbiologically Influenced Corrosion,” CORROSION/2007, paper no. 07515 (Houston, TX: NACE, 2007). 19. R. Sooknah, S. Papavinasam, R.W. Revie, “Validation of a Predictive Model for Microbiologically Influenced Corrosion,” CORROSION/2008, paper no. 08503 (Houston, TX: NACE, 2008). 20. NACE TM0194 (latest revision), “Field Monitoring of Bacterial Growth in Oil and Gas Systems” (Houston, TX: NACE). 21. Standard Methods for the Examination of Water and Wastewater (latest revision), American Public Health Association (2) (3) (4) (APHA), American Water Works Association (AWWA), and Water Environment Federation (WEF) (Washington, DC: APHA; Denver, CO: AWWA; and Alexandria, VA: WEF). 22. P.J.B. Scott, et al., “Expert Consensus on MIC: Prevention and Monitoring—Part 1,” MP 43, 3 (2004): p. 50.

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American Public Health Association (APHA), 800 I St. NW, Washington, DC 20001. American Water Works Association (AWWA), 6666 W. Quincy Ave., Denver, CO 80235. (4) Water Environment Federation (WEF), 601 Wythe Street, Alexandria, VA 22314-1994. (3)

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TM0212-2012 23. J. Larsen, T.L. Skovhus, M. Agerbæk, T.R. Thomsen, P.H. Nielsen, “Bacterial Diversity Study Applying Novel Molecular Methods on Halfdan Produced Waters,” CORROSION/2006, paper no. 06668 (Houston, TX: NACE, 2006). 24. J. Larsen, et al., “Identification of Bacteria Causing Souring and Biocorrosion in the Halfdan Field by Application of New Molecular Techniques,” CORROSION/2005, paper no. 05629 (Houston, TX: NACE, 2005). 25. D.H. Pope, T.P. Zintel, “Methods for the Investigation of Under-Deposit Microbiologically Influenced Corrosion,” CORROSION/88, paper no. 88249 (Houston, TX: NACE, 1988), pp. 1-17. 26. X. Zhu, et al., “Improved Method for Monitoring Microbial Communities in Gas Pipelines,” CORROSION/2004, paper no. 04592 (Houston, TX: NACE, 2004), pp. 1-13. 27. T.L. Skovhus, et al., “Practical Use of New Microbiology Tools in Oil Production,” SPE Offshore Europe Conference 2007, paper no. SPE 109104 (Aberdeen, UK: SPE, 2007). 28. X.Y. Zhu, A. Ayala, H. Modi, J.J. Kilbane II, “Applications of Quantitative, Real-Time PCR in Monitoring Microbiologically Influenced Corrosion (MIC) in Gas Pipelines,” CORROSION/2005, paper no. 05493 (Houston, TX: NACE, 2005), pp. 1-15. 29. K. Sørensen, T.L. Skovhus, J. Larsen, “Techniques for enumerating microorganisms in oilfields,” in International Symposium on Applied Microbiology and Molecular Biology in Oilfield Systems (ISMOS-2), C. Whitby, T.L. Skovhus, eds. (New York, NY: Springer, 2009). 30. K. Takai, K. Horikoshi, “Rapid Detection and Quantification of Members of the Archaeal Community by Quantitative PCR Using Fluorogenic Probes,” Applied and Environmental Microbiology 66, 11 (2000): pp. 5066-5076. 31. T.L. Skovhus, N.B. Ramsing, C. Holmstrom, S. Kjelleberg, I. Dahllof, “Real-Time Quantitative PCR for Assessment of Abundance of Pseudoalteromonas Species in Marine Samples,” AEM 70, 4 (2004): pp. 2373-2382. 32. J. Larsen, T.L. Skovhus, A.M. Saunders, B. Højris, M. Agerbæk, “Molecular Identification of MIC Bacteria from Scale and Produced Water: Similarities and Differences,” CORROSION/2008, paper no. 08652 (Houston, TX: NACE, 2008). 33. V.V. Keasler, et al., “Identification and Analysis of Biocides Effective Against Sessile Organisms,” SPE International Symposium on Oilfield Chemistry 2009, paper no. 121082 (Aberdeen, UK: SPE, 2009). 34. NACE Standard RP0775 (latest revision), “Preparation, Installation, Analysis, and Interpretation of Corrosion Coupons in Oilfield Operations” (Houston, TX: NACE). 35. ASTM G46 (latest revision), “Standard Guide for Examination and Evaluation of Pitting Corrosion” (West Conshohocken, PA: ASTM, 2006). 36. M. Attard, et al., “Comparison of Pitting Corrosion Rates of Coupons and Pipes,” MP 39, 10 (Houston, TX: NACE, 2000): p. 58. 37. R.B. Eckert, H.C. Aldrich, C.A. Edwards, B.A. Cookingham, “Microscopic Differentiation of Internal Corrosion Initiation Mechanisms in Natural Gas Pipeline Systems,” CORROSION/2003, paper no. 03544 (Houston, TX: NACE, 2003). 38. R. Eckert, B. Cookingham, “Field Use Proves Program for Managing Internal Corrosion in Wet-Gas Systems,” Oil Gas J. 100, 3 (2002). 39. T.P. Zintel, D.A. Kostuck, B.A. Cookingham, “Evaluation of Chemical Treatments in Natural Gas Systems vs. MIC and Other Forms of Internal Corrosion Using Carbon Steel Coupons,” CORROSION/2003, paper no. 03574 (Houston, TX: NACE, 2003). 40. N.J.E. Dowling, M.W. Mittelman, J.C. Danko, Microbially Influenced Corrosion and Biodeterioration (Knoxville, TN: University of Tennessee Press, 1991): pp. 5-57–5-64. 41. B.G. Pound, S. Brossia, O. Moghissi, N. Sridhar, “Differentiation of Corrosion Mechanisms by Morphological Feature (5) Characterization” (Des Plaines, IL: Gas Technology Institute, 2004).

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Gas Technology Institute, 1700 S. Mount Prospect Road, Des Plaines, IL 60018-1804.

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TM0212-2012 42. J. Larsen, K. Sorensen, B. Hojris, T.L. Skovhus, “Significance of Troublesome Sulfate-Reducing Prokaryotes (SRP) in Oilfield Systems,” CORROSION/2009, paper no. 09389 (Houston, TX: NACE, 2009), p. 12, Table 1. 43. R.B. Eckert, H.C. Aldrich, C.A. Edwards, C. Yang, M. Yunovich, “Development of a Bench Test Method for Microbiologically (6) Influenced Corrosion (MIC),” (Falls Church, VA: Pipeline Research Council International (PRCI), 2005). 44. R.B. Eckert, H.C. Aldrich, C.A. Edwards, C. Yang, “Guidelines for Reproducing Microbiologically Influenced Corrosion Initiation on Carbon Steels Under Controlled Conditions,” CORROSION/2006, paper no. 06519 (Houston, TX: NACE, 2006). 45. NACE Publication 3T199 (latest revision), “Techniques for Monitoring Corrosion and Related Parameters in Field Applications” (Houston, TX: NACE). 46. R. Sooknah, et al., “An Electrochemical Biosensor Designed for Online Monitoring of Sulfate Reducing Bacteria,” JAI 5, 6 (West Conshohocken, PA: ASTM, 2008): p. 10. 47. R. Sooknah, S. Papavinasam, R.W. Revie, “Sulfide Oxidase Biosensor for Monitoring Sulfide,” CORROSION 2008, paper no. 08656 (Houston, TX: NACE, 2008). 48. T. Haile, R. Sooknah, S. Papavinasam, D. Gould, O. Dinardo, “Simultaneous Online Monitoring of SRB Activity and Corrosion Rate,” CORROSION 2010, paper no. 10255 (Houston, TX: NACE, 2010). 49. NACE SP0206 (latest revision), “Internal Corrosion Direct Assessment Methodology for Pipelines Carrying Normally Dry Natural Gas (DG-ICDA)” (Houston, TX: NACE). 50. NACE SP0208 (latest revision), “Internal Corrosion Direct Assessment Methodology for Liquid Petroleum Pipelines” (Houston, TX: NACE). 51. NACE SP0110 (latest revision), “Wet Gas Internal Corrosion Direct Assessment Methodology for Pipelines” (Houston, TX: NACE). 52. B.F.M. Pots, et al., “Improvements on De Waard-Milliams Corrosion Prediction and Applications to Corrosion Management,” CORROSION/2002, paper no. 02235 (Houston, TX: NACE, 2002). 53. S. Maxwell, S. Campbell, “Monitoring the Mitigation of MIC Risk in Pipelines,” CORROSION/2006, paper no. 06662 (Houston, TX: NACE, 2006). 54. NACE SP0106 (latest revision), “Control of Internal Corrosion in Steel Pipelines and Piping Systems” (Houston, TX: NACE).

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Pipeline Research Council International (PRCI), 3141 Fairview Park Drive, Suite 525, Falls Church, VA 22042.

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TM0212-2012 _________________________________________________________________________ Appendix A Site Inspection and Testing Checklist (Nonmandatory) This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

A sample checklist used for site inspection and testing is provided in Table A1.

Table A1 Site Inspection and Testing Checklist Data Type Observations/Notes Sample location Relationship of sample to: Distance from nearest compressor station Inlets, outlets, taps, fittings Heat sources or temperature change Construction/material changes Recent repairs or damage Other pipelines or underground facilities Observations before sampling Location and distribution of solids, scale, deposits, or other material visible on the walls of the pipe section or component being sampled, relative to the collected samples Characteristics of the surface-associated material: dry, moist, or wet; silt, sand; odor; color; texture, layering, or strata; at different locations on the internal surface, relative to any samples collected Relationship of any corroded area to the sampled surface-associated materials Physical location in the pipeline; clock position, relationship to damage observed in an internal coating; position of samples relative to disturbance or contamination that occurred during handling of the pipeline sample Measurements before sampling Temperature pH Pressure Flow rate Observations during sampling Color changes Odors Observations after sampling Extent of corrosion damage (length, circumference, area of pipeline exposed) NACE International

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TM0212-2012 Data Type Location of corrosion damage relative to pipeline girth and seam welds, and coating seam if applicable Typical location of corrosion damage (top, bottom, sides, random) Corrosion products/deposits color Nature of deposits (scale, nodule, film) Deposit texture (hard, soft, friable) Deposit odor Deposit strata (note changes in layers if they exist) Visual differences between general deposits and localized deposits associated with corrosion Relationship between coating and deposits (e.g., beneath coating, on top of coating) Scale present? Chemical spot testing results - Sulfides - Carbonates Location of all deposit samples collected for analysis Visible biological accumulations in deposits or on pipe Liquid present beneath deposits? pH of liquid beneath deposits Observations of corrosion damage Nature of corrosion damage Isolated pitting Isolated pitting within areas of general corrosion Linked pitting within areas of general corrosion General metal loss with few deeper pits Etching or general metal loss with no pitting Selective attack at welds Crevice corrosion (at flange joints, mechanical joints) Pit morphology (elliptical, parabolic, narrow, grain attack, subsurface) See Figure 1. Pit features (striations, tunnels, cup shape, pits within pits, undercutting, strata levels, grooves, shiny, dull) Other observations Severity of corrosion: Longitudinal extent Circumferential extent Maximum wall loss Profile of wall loss Maximum/average pit depth Maximum/average pit diameter Where is corrosion most severe? Samples collected for microbial and chemical analysis—type and volume

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Observations/Notes

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TM0212-2012 Data Type Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Internal coating/deposit samples a. Disbonded or damaged coating b. Deposits at corrosion sites c. Deposits where no corrosion occurred d. Scale, biofilm, liquids from under coating Corrosion samples a. Corrosion products or nodules b. Material from beneath nodules c. Surface swab of pit contents d. Pipe sample cut-out General information and history Year of installation Pipeline diameter and wall thickness Pipeline grade and manufacturer Inspection history Corrosion mitigation programs Corrosion monitoring results Leak/failure history Operational problems Microbiological monitoring results Fluid characteristics Integrity assessment results (ILI, ICDA) Maintenance pigging history

Observations/Notes

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TM0212-2012 _________________________________________________________________________ Appendix B Example of Pipeline System Assay Data (Nonmandatory) This appendix is considered nonmandatory, although it may contain mandatory language. It is intended only to provide supplementary information or guidance. The user of this standard is not required to follow, but may choose to follow, any or all of the provisions herein.

Examples of data that may be collected and used as part of a system assay are provided in Table B1. These data may be used to identify areas where additional information or testing is needed, and for integration and analysis to determine the threat of MIC.

Table B1 Example Pipeline System Assay Data Category Example Data Historical changes in flow direction, type of service, product Operating and design history composition, added or removed taps, age of equipment Length between inputs/outputs of the pipeline system being Defined length assayed (7) Topographical data (e.g., U.S. Geological Survey [USGS] data), including consideration of pipeline depth of cover. Data should Elevation profile provide sufficient accuracy and precision to facilitate flow models, if used Locations of roads, rivers, drains, valves, drips, processing Key features equipment or facilities, aerial crossings, pig launchers and receivers Nominal pipe diameter and wall thickness of pipe, grade of material, Pipe specifications age of material, process of manufacture Pressure Flow rate Temperature Dew point

Typical, minimum and maximum operating pressures Maximum and minimum flow rates at various operating pressures for all inlets and outlets, periods of low or no flow should be noted Ambient soil temperature, compressor or pump discharge temperature Water vapor and liquid hydrocarbon dew points

Identify all locations of current and historic inputs and outputs to the system Corrosion inhibitor, biocide, Injection location, rates, chemical types, frequency of application, and process chemical chemical quality and testing records, history of chemical tankage additions and handling relative to potential for contamination or degradation Frequency, nature of upset (intermittent or chronic), volume, and Process upsets nature of liquids or solids introduced by upset Identify process equipment that affects the characteristics or Process equipment composition of the primary contents of the pipeline (e.g., dehydrators, scrubbers, filters, settlement tanks, treaters) Identify source of water, water quality data, treatment used, length Hydrostatic testing of time water remained in pipeline, subsequent dewatering processes Cleaning pig records, type of pig used, frequencies, length of run, Maintenance number of runs, and dates. Volume, nature, and analytical data of Inputs/outputs

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U.S. Geological Survey (USGS), 12201 Sunrise Valley Dr., Reston, VA 20192.

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TM0212-2012 sludge or liquids received or from liquid separators associated with pigging Inspection records identifying the locations, frequency, and severity Inspection and repair of internal features or verified corrosion, pipe section or component repair and replacement records Location, type, and reason for abandonment or decommissioning of Decommissioning related (upstream, downstream, loops, inputs, outlets) pipe or equipment Locations, frequency, dates and nature of leaks/failures, root cause Leaks/failures or failure investigation records Gas and liquid analysis results for the pipeline, and on shipper and Product quality delivery laterals, relationship of gas or liquid analyses to pipeline segment being assayed Corrosion monitoring data including type of monitoring (e.g., coupons, ER/LPR probes), dates and relationship of monitoring to Corrosion monitoring pipe being assayed, corrosion rate, pitting rate, and photographs of coupons Existence, type, and location(s) of internal coatings, including flow Internal coating coatings If single or multiphase flow modeling has been performed, these Flow modeling data should be considered in the system assay Results of integrity assessments such as from ILI, ICDA, or Integrity assessment hydrostatic testing Microbiological testing on Results of previous monitoring (e.g., MPN data from liquid culture liquids media testing, or enzyme tests) Microbiological testing on Results of previous monitoring (e.g., MMM data obtained from biofilms surfaces, studs, pigging debris, corrosion products, and biofilms) Records of previous internal visual inspections of pipe or related Visual inspection tanks or vessels, photographs, corrosion damage observed, presence of solids, sulfide odor Flow restriction, loss of production or injectivity, increased presence Operational problems of solids or sludge, souring, pressure drop, etc. Results of corrosion rate models, type of model used, data input to Corrosion rate models the model Results of models used to predict the location and severity of Corrosion prediction models internal corrosion, data sources used Original and revised design life information, calculations, and Design life models Information about the pipeline fluids and specific concerns to the Health, safety, environment environments where field tests could be performed

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TM0212-2012

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ISBN 1-57590-255-9 NACE International

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